Nearshore Marine Ecosystem Research Active
Nearshore ecosystems include many resources that are of high ecological, recreational, subsistence, and economic value. They also are subject to influences from a wide variety of natural and human-caused perturbations, which can originate in terrestrial or oceanic environments. Our research is designed to evaluate sources of variation in the nearshore and how they influence resources of high conservation interest.
Return to Ecosystems >> Marine Ecosystems
Sea Otter Population Assessment
With the exception of 13 small remnant populations, sea otters were extirpated from their historic range in the north Pacific Ocean during the 18th and 19th centuries as a result of the commercial harvest for their fur. During most of the 20th century, through protection and reintroduction, sea otter populations generally increased in abundance and distribution such that most of their range in Alaska, with the exception of southeast Alaska, was occupied by 2000. Although population abundance data are incomplete, there is evidence of increasing, stable and declining sea otter populations in different areas within their range. The factors that ultimately regulate sea otter population abundance are not completely understood, but can include predation, human harvest, food limitation, disease and catastrophic events such as oil spill. There is good evidence that the recent declines in sea otters in SW Alaska are related to killer whale predation and the Exxon Valdez oil spill reduced the size of the western Prince William Sound population in 1989. Human harvest of sea otters can adversely affect sea otter abundance, evidenced by the commercial fur trade leading to near extirpation. Because sea otters occupy relatively small home ranges and do not migrate, sustainable harvest requires management at appropriate spatial scales. Recently, harvest of sea otters for subsistence have been increasing, although effects of the harvest at current levels on population trend are unknown. Because sea otter populations occur over vast and remote areas and may display divergent trends in abundance over relatively small spatial scales, determining population status and trends can be challenging.
Methods to assess sea otter population status and trends are important to evaluate the recovery of populations and the potential effects of human perturbations (e.g., harvest, contaminants, and habitat modifications) on populations. This information is important to resource managers in identifying potential conflicts, identifying mechanisms of change, and improving the ability to detect and respond to change from human induced sources.
Objectives of our sea otter population assessment studies include: 1) develop and test methods to identify the degree of population structuring among north Pacific sea otter populations, 2) develop and test techniques to accurately and precisely estimate the status of sea otter populations, 3) develop and test methods to identify cause(s) of change in the status and numeric trends of sea otter populations, 4) develop and test methods to determine the role of density dependent processes in affecting change in sea otter populations, and 5) evaluate the effects of population reductions and translocations on sea otter genetic variability.
Role of Sea Otters in Structuring Nearshore Communities
Sea otters provide one of the best documented examples of top-down forcing effects on the structure and function of nearshore marine ecosystems in the North Pacific Ocean. Much of our knowledge of the role of sea otters as a source of community variation resulted from the spatial and temporal pattern of sea otter population recovery since their near extirpation about 100 years ago. During most of the early 20th century sea otters were absent from large portions of their habitat in the north Pacific. During the absence of sea otters, many of their prey populations responded to reduced predation through increased densities and sizes. Since the middle of the 20th century sea otter populations have been recovering previous habitats, due to natural dispersal and translocations. Following the recovery of sea otters, scientists have continued to provide descriptions of nearshore marine communities and have been able to contrast those communities before and after the sea otters return. At least three distinct approaches have proven valuable in understanding the effects of sea otters. One is contrasting communities over time, before and after recolonization by sea otters. This approach, in concert with appropriate controls, provides an experimentally rigorous and powerful study design allowing inference to the cause of the observed changes in experimental areas. Another approach consists of contrasting different areas at the same time, those with, and those without the experimental treatment (in this case, sea otters). A third approach entails experimentally manipulating community attributes and observing community response, usually in both treatment and control areas. All these opportunities currently present themselves at various locations throughout the sea otters’ range.
One area of recent reoccupation is Glacier Bay in Southeast Alaska, where sea otters were absent until as recently as 1994, but currently number > 4000 individuals. We are using this situation in Glacier Bay as a laboratory to experimentally evaluate the role of sea otter in structuring coastal marine communities in a predominately soft sediment habitat. It is predictable that the density and sizes of preferred sea otter prey such as crabs, clams, and urchins will decline in response to otter predation. This will result in fewer opportunities for human harvest, but will also result in ecosystem level changes, as abundance and sizes of prey for other predators, such as octopus, sea stars, fishes, birds and mammals are modified. Sea otters will also modify benthic habitats through excavation of sediments required to extract burrowing infauna such as clams. Effects of sediment disturbance by foraging sea otters are not understood. As the recolonization by sea otters continues, it is also likely that dramatic changes will occur in the species composition, abundance and size class composition of many components of the nearshore marine ecosystem. Many of the changes will occur as a direct result of predation by sea otters; other changes will result from indirect or cascading effects of sea otter foraging, such as increasing kelp production and modified prey availability for other nearshore predators.
Effects of the Exxon Valdez Oil Spill
Sea otters were severely impacted by the 1989 Exxon Valdez oil spill. Estimates of acute spill related mortality range from about 1,000 to 5,500 in the first months after the spill. Scientists with the Alaska Science Center were among the first responders to the 1989 spill and continue work today to document the process of recovery form this spill and to better understand the effects future contamination events on sea otters and the nearshore ecosystems they occupy.
One of the factors limiting our ability to clearly understand and document the spill effects was a lack of accurate estimates of sea otter abundance. This was true for nearly all species in the Gulf of Alaska and remains an impediment in assessing injury from such catastrophes across most landscapes today. Initial research efforts following the spill focused on damage assessment, including developing methods to accurately estimate the abundance of affected populations and studies of reproduction and survival.
Large scale ecosystem level studies of nearshore species and habitats most affected by the spill completed in 1999, found evidence of long-term spill effects among nearshore species dependent on a nearshore food web where benthic invertebrates transfer primary production to upper level consumers such as sea otters and sea ducks. Biochemical and gene techniques suggested that lingering oil may have contributed to a protracted recovery period for nearshore species. Subsequently, surveys of beaches where oil was deposited nearly a decade earlier found unanticipated volumes of oil sequestered in nearly 20 acres of widely distributed soft sediment intertidal beaches in Prince William Sound.
Our most recent surveys of sea otter abundance indicate significant progress toward recovery, when we consider the entire spill affected area in the Sound. By 2009 our estimate of sea otter abundance in the western Sound was nearly 2,000 animals more than our first post spill estimate in 1993 of about 2,000 individuals. However, when we look only at those areas that were most severely affected by the spill, where sea otter mortality approached 90% and where much of the lingering oil has been located, evidence of recovery remains incomplete. Our most recent research, based on the diving behavior of sea otters in the intertidal and published oil encounter rates, indicates that all sea otters in those heavily oiled areas are likely to encounter Exxon Valdez oil at least annually and some as often as weekly. Long term continuation of studies investigating mortality from the annual collections of beach cast sea otter carcasses implicates elevated mortality as the factor most likely contributing to delayed recovery, and suggests that chronic mortality after the spill may meet or exceed the acute mortality experienced after the spill.
Lingering Oil Studies
Sea otters were severely impacted by the 1989 Exxon Valdez oil spill. Estimates of acute spill related mortality range from about 1,000 to 5,500 in the first months after the spill. Scientists with the Alaska Science Center were among the first responders to the 1989 spill and continue work today to document the process of recovery form this spill and to better understand the effects future contamination events on sea otters and the nearshore ecosystems they occupy.
One of the factors limiting our ability to clearly understand and document the spill effects was a lack of accurate estimates of sea otter abundance. This was true for nearly all species in the Gulf of Alaska and remains an impediment in assessing injury from such catastrophes across most landscapes today. Initial research efforts following the spill focused on damage assessment, including developing methods to accurately estimate the abundance of affected populations and studies of reproduction and survival.
Large scale ecosystem level studies of nearshore species and habitats most affected by the spill completed in 1999, found evidence of long-term spill effects among nearshore species dependent on a nearshore food web where benthic invertebrates transfer primary production to upper level consumers such as sea otters and sea ducks. Biochemical and gene techniques suggested that lingering oil may have contributed to a protracted recovery period for nearshore species. Subsequently, surveys of beaches where oil was deposited nearly a decade earlier found unanticipated volumes of oil sequestered in nearly 20 acres of widely distributed soft sediment intertidal beaches in Prince William Sound.
Our most recent surveys of sea otter abundance indicate significant progress toward recovery, when we consider the entire spill affected area in the Sound. By 2009 our estimate of sea otter abundance in the western Sound was nearly 2,000 animals more than our first post spill estimate in 1993 of about 2,000 individuals. However, when we look only at those areas that were most severely affected by the spill, where sea otter mortality approached 90% and where much of the lingering oil has been located, evidence of recovery remains incomplete. Our most recent research, based on the diving behavior of sea otters in the intertidal and published oil encounter rates, indicates that all sea otters in those heavily oiled areas are likely to encounter Exxon Valdez oil at least annually and some as often as weekly. Long term continuation of studies investigating mortality from the annual collections of beach cast sea otter carcasses implicates elevated mortality as the factor most likely contributing to delayed recovery, and suggests that chronic mortality after the spill may meet or exceed the acute mortality experienced after the spill.
Long-term Monitoring
The Alaska Science Center, and in preceding Department of Interior agencies, has been engaged in monitoring various sea otter populations for more than 50 years, since Karl Kenyon’s seminal work in the Aleutian Islands. As sea otter populations have recovered from the fur trade and translocations contributed to expanding populations, the task of sea otter monitoring has become increasingly difficult simply because of the vast and remote nature of sea otter habitat. Moreover, it has become increasingly evident that monitoring of single species, while perhaps necessary for management purposes, often provides little insight as to why changes in abundance occur over time. As a result we have been engaged in the development, design and testing of monitoring protocols for nearshore habitats and species, including sea otters, that might best be described as “ecosystem” or “food web” based monitoring.
The nearshore is considered an important component of the Gulf of Alaska ecosystem, including the region affected by the Exxon Valdez oil spill, because it provides:
- A variety of unique habitats for resident organisms (e.g. sea otters, harbor seals, shorebirds, seabirds, nearshore fishes, kelps, seagrasses, clams, mussels, and sea stars).
- Nursery grounds for marine animals from other habitats (e.g. crabs, salmon, herring, and seabirds).
- Feeding grounds for important consumers, including killer whales, harbor seals, sea otters, sea lions, sea ducks, shore birds and many fish and shellfish.
- A source of animals important to commercial and subsistence harvests (e.g. marine mammals, fishes, crabs, mussels, clams, chitons, and octopus).
- An important site of recreational activities including fishing, boating, camping, and nature viewing.
- A source of primary production for export to adjacent habitats (primarily by kelps, other seaweeds, and eelgrass), as well as a recipient for primary (phytoplankton) and secondary production (zooplankton) transported from offshore systems..
- An important triple interface between air, land and sea that provides linkages for transfer of water, nutrients, and species between watersheds and offshore habitats.
The underlying assumption in our monitoring design is that change will occur, and that careful consideration of what to monitor, may eventually provide insight as to why observed change occurred. In the nearshore ecosystem we work in, primary productivity is provided by at least two independent sources, the micro-algae, or phytoplankton, that occurs near the sea surface and may be transported inshore via currents. The second, and sometimes major contributor to total primary production is through the kelps and sea grasses that are conspicuous features of the nearshore zone. These combined sources of carbon fuel a diverse community of invertebrates, such as mussels, clams, snails, crustaceans, and urchins, that ultimately transfer their energy to various higher trophic level invertebrates and vertebrates, such as fishes, birds (shore birds, sea ducks and others) and mammals (primarily sea otters). Through careful selection of species and processes (growth, survival and diet) we expect to gain a better understanding of the interaction between various trophic levels that will allow us to potentially assign cause to some of the change we expect to see over time.
As part of the planning efforts of the Exxon Valdez Trustee Council for a long-term science program, in 2001 we were tasked to develop a science and monitoring program for the nearshore ecosystem in the Gulf of Alaska. Through a process of workshops and consultations we developed the Nearshore Restoration and Ecosystem Monitoring program (N-REM, Dean and Bodkin 2006). Coincident with our planning efforts for the Exxon Valdez Trustte Council, the National Park Service was implementing a strategy known as “vital signs monitoring” to develop scientifically sound information on the status and long-term trends of park ecosystems and to determine how well current management practices are sustaining those ecosystems. Subsequently, Park managers from the Southwest Alaska Network (SWAN) recognized that the program we designed for the Exxon Valdez Trustee Council fit their Vital Signs needs and a new partnership was established to implement long term monitoring in the nearshore marine habitat of the SWAN parks.
SWAN consists of five Alaskan park units (Aniakchak National Monument and Preserve, Alagnak National Wild River, Katmai National Park and Preserve, Kenai Fjords National Park, and Lake Clark National Park and Preserve). Collectively these units comprise 9.4 million acres or 11.6 percent of the total land area managed by the National Park Service. Network parks encompass climatic conditions, geologic features, near pristine ecosystems, natural biodiversity, freshwater, and marine resources equaled few places in North America. This network of relatively untouched wilderness parks is a unique resource and offers unparalleled opportunities to study and monitor ecological systems minimally affected by humans. In recognition of this, the SWAN monitoring framework emphasizes (i) establishing reference conditions representing the current status of park, monument, and preserve ecosystems; and (ii) detecting ecological change through time. In 2008, The Exxon Valdez Trustee Council adopted and implemented our nearshore monitoring design in Prince William Sound, extending the SWAN nearshore program from the Gulf of Alaska into Prince William Sound and Kachemak Bay in Cook Inlet. The Gulf of Alaska nearshore monitoring program now consists of four primary sites, including Prince William Sound, Kenai Fjords National Park, Kachemak Bay and Katmai National Park.
Below are data or web applications associated with this project.
Morphometric and Reproductive Status Data for Sea Otters Collected or Captured in Alaska
Sea Otter Aerial Survey Data from Southeast Alaska, 2002-2003
Gulf Watch Alaska Nearshore Component: Sea Otter Aerial Survey Data Katmai National Park and Preserve, 2008 - 2018 (ver 2.0, March 2020)
Gulf Watch Alaska, Nearshore Component: Sea Otter Mortality Age Data from Katmai National Park and Preserve, Kenai Fjords National Park, and Prince William Sound, Alaska, 2006-2017
Sea Otter Aerial Survey Data from Glacier Bay National Park and Preserve, 1999-2012
Intertidal Soft-Sediment Bivalves from Prince William Sound, Kachemak Bay, Katmai National Park and Preserve, and Kenai Fjords National Park
Gulf Watch Alaska Nearshore Component: Marine Bird and Mammal Survey Data from Katmai National Park and Preserve and Kenai Fjords National Park, 2012-2016
Gulf Watch Alaska Nearshore Component: Sea Otter Aerial Survey Data Kenai Fjords National Park, 2002-2016
Sea Otter Gene Transcription Data from Kodiak, the Alaska Peninsula, and Prince William Sound, Alaska, 2005-2012
Gulf Watch Alaska, Nearshore Monitoring Component: Sea Otter Foraging Observations from Prince William Sound, Katmai National Park and Preserve, and Kenai Fjords National Park, 2012-2016
Black Oystercatcher Nest and Diet Data from Kachemak Bay, Katmai National Park and Preserve, Kenai Fjords National Park, and Prince William Sound
Gulf Watch Alaska Nearshore Component: Monitoring Site Locations from Prince William Sound, Katmai National Park and Preserve, and Kenai Fjords National Park
Below are multimedia items associated with this project.
Below are publications associated with this project.
Keystone predators govern the pathway and pace of climate impacts in a subarctic marine ecosystem
Trends and carrying capacity of sea otters in Southeast Alaska
Variation in abundance of Pacific Blue Mussel (Mytilus trossulus) in the Northern Gulf of Alaska, 2006–2015
Cessation of oil exposure in harlequin ducks after the Exxon Valdez oil spill: Cytochrome P4501A biomarker evidence
Widespread kelp-derived carbon in pelagic and benthic nearshore fishes
Gene transcript profiling in sea otters post-Exxon Valdez oil spill: A tool for marine ecosystem health assessment
Influence of basin- and local-scale environmental conditions on nearshore production in the northeast Pacific Ocean
Influence of static habitat attributes on local and regional Rocky intertidal community structure
Monitoring population status of sea otters (Enhydra lutris) in Glacier Bay National Park and Preserve, Alaska: options and considerations
The interaction of intraspecific competition and habitat on individual diet specialization: a near range-wide examination of sea otters
Evaluating the status of individuals and populations: Advantages of multiple approaches and time scales
Timelines and mechanisms of wildlife population recovery following the Exxon Valdez Oil Spill
Below are news stories associated with this project.
- Overview
Nearshore ecosystems include many resources that are of high ecological, recreational, subsistence, and economic value. They also are subject to influences from a wide variety of natural and human-caused perturbations, which can originate in terrestrial or oceanic environments. Our research is designed to evaluate sources of variation in the nearshore and how they influence resources of high conservation interest.
Return to Ecosystems >> Marine Ecosystems
Sea Otter Population Assessment
With the exception of 13 small remnant populations, sea otters were extirpated from their historic range in the north Pacific Ocean during the 18th and 19th centuries as a result of the commercial harvest for their fur. During most of the 20th century, through protection and reintroduction, sea otter populations generally increased in abundance and distribution such that most of their range in Alaska, with the exception of southeast Alaska, was occupied by 2000. Although population abundance data are incomplete, there is evidence of increasing, stable and declining sea otter populations in different areas within their range. The factors that ultimately regulate sea otter population abundance are not completely understood, but can include predation, human harvest, food limitation, disease and catastrophic events such as oil spill. There is good evidence that the recent declines in sea otters in SW Alaska are related to killer whale predation and the Exxon Valdez oil spill reduced the size of the western Prince William Sound population in 1989. Human harvest of sea otters can adversely affect sea otter abundance, evidenced by the commercial fur trade leading to near extirpation. Because sea otters occupy relatively small home ranges and do not migrate, sustainable harvest requires management at appropriate spatial scales. Recently, harvest of sea otters for subsistence have been increasing, although effects of the harvest at current levels on population trend are unknown. Because sea otter populations occur over vast and remote areas and may display divergent trends in abundance over relatively small spatial scales, determining population status and trends can be challenging.
Methods to assess sea otter population status and trends are important to evaluate the recovery of populations and the potential effects of human perturbations (e.g., harvest, contaminants, and habitat modifications) on populations. This information is important to resource managers in identifying potential conflicts, identifying mechanisms of change, and improving the ability to detect and respond to change from human induced sources.
Objectives of our sea otter population assessment studies include: 1) develop and test methods to identify the degree of population structuring among north Pacific sea otter populations, 2) develop and test techniques to accurately and precisely estimate the status of sea otter populations, 3) develop and test methods to identify cause(s) of change in the status and numeric trends of sea otter populations, 4) develop and test methods to determine the role of density dependent processes in affecting change in sea otter populations, and 5) evaluate the effects of population reductions and translocations on sea otter genetic variability.
Role of Sea Otters in Structuring Nearshore Communities
Sea otters provide one of the best documented examples of top-down forcing effects on the structure and function of nearshore marine ecosystems in the North Pacific Ocean. Much of our knowledge of the role of sea otters as a source of community variation resulted from the spatial and temporal pattern of sea otter population recovery since their near extirpation about 100 years ago. During most of the early 20th century sea otters were absent from large portions of their habitat in the north Pacific. During the absence of sea otters, many of their prey populations responded to reduced predation through increased densities and sizes. Since the middle of the 20th century sea otter populations have been recovering previous habitats, due to natural dispersal and translocations. Following the recovery of sea otters, scientists have continued to provide descriptions of nearshore marine communities and have been able to contrast those communities before and after the sea otters return. At least three distinct approaches have proven valuable in understanding the effects of sea otters. One is contrasting communities over time, before and after recolonization by sea otters. This approach, in concert with appropriate controls, provides an experimentally rigorous and powerful study design allowing inference to the cause of the observed changes in experimental areas. Another approach consists of contrasting different areas at the same time, those with, and those without the experimental treatment (in this case, sea otters). A third approach entails experimentally manipulating community attributes and observing community response, usually in both treatment and control areas. All these opportunities currently present themselves at various locations throughout the sea otters’ range.
One area of recent reoccupation is Glacier Bay in Southeast Alaska, where sea otters were absent until as recently as 1994, but currently number > 4000 individuals. We are using this situation in Glacier Bay as a laboratory to experimentally evaluate the role of sea otter in structuring coastal marine communities in a predominately soft sediment habitat. It is predictable that the density and sizes of preferred sea otter prey such as crabs, clams, and urchins will decline in response to otter predation. This will result in fewer opportunities for human harvest, but will also result in ecosystem level changes, as abundance and sizes of prey for other predators, such as octopus, sea stars, fishes, birds and mammals are modified. Sea otters will also modify benthic habitats through excavation of sediments required to extract burrowing infauna such as clams. Effects of sediment disturbance by foraging sea otters are not understood. As the recolonization by sea otters continues, it is also likely that dramatic changes will occur in the species composition, abundance and size class composition of many components of the nearshore marine ecosystem. Many of the changes will occur as a direct result of predation by sea otters; other changes will result from indirect or cascading effects of sea otter foraging, such as increasing kelp production and modified prey availability for other nearshore predators.
Effects of the Exxon Valdez Oil Spill
Sea otters were severely impacted by the 1989 Exxon Valdez oil spill. Estimates of acute spill related mortality range from about 1,000 to 5,500 in the first months after the spill. Scientists with the Alaska Science Center were among the first responders to the 1989 spill and continue work today to document the process of recovery form this spill and to better understand the effects future contamination events on sea otters and the nearshore ecosystems they occupy.
One of the factors limiting our ability to clearly understand and document the spill effects was a lack of accurate estimates of sea otter abundance. This was true for nearly all species in the Gulf of Alaska and remains an impediment in assessing injury from such catastrophes across most landscapes today. Initial research efforts following the spill focused on damage assessment, including developing methods to accurately estimate the abundance of affected populations and studies of reproduction and survival.
Large scale ecosystem level studies of nearshore species and habitats most affected by the spill completed in 1999, found evidence of long-term spill effects among nearshore species dependent on a nearshore food web where benthic invertebrates transfer primary production to upper level consumers such as sea otters and sea ducks. Biochemical and gene techniques suggested that lingering oil may have contributed to a protracted recovery period for nearshore species. Subsequently, surveys of beaches where oil was deposited nearly a decade earlier found unanticipated volumes of oil sequestered in nearly 20 acres of widely distributed soft sediment intertidal beaches in Prince William Sound.
Our most recent surveys of sea otter abundance indicate significant progress toward recovery, when we consider the entire spill affected area in the Sound. By 2009 our estimate of sea otter abundance in the western Sound was nearly 2,000 animals more than our first post spill estimate in 1993 of about 2,000 individuals. However, when we look only at those areas that were most severely affected by the spill, where sea otter mortality approached 90% and where much of the lingering oil has been located, evidence of recovery remains incomplete. Our most recent research, based on the diving behavior of sea otters in the intertidal and published oil encounter rates, indicates that all sea otters in those heavily oiled areas are likely to encounter Exxon Valdez oil at least annually and some as often as weekly. Long term continuation of studies investigating mortality from the annual collections of beach cast sea otter carcasses implicates elevated mortality as the factor most likely contributing to delayed recovery, and suggests that chronic mortality after the spill may meet or exceed the acute mortality experienced after the spill.
Lingering Oil Studies
Sea otters were severely impacted by the 1989 Exxon Valdez oil spill. Estimates of acute spill related mortality range from about 1,000 to 5,500 in the first months after the spill. Scientists with the Alaska Science Center were among the first responders to the 1989 spill and continue work today to document the process of recovery form this spill and to better understand the effects future contamination events on sea otters and the nearshore ecosystems they occupy.
One of the factors limiting our ability to clearly understand and document the spill effects was a lack of accurate estimates of sea otter abundance. This was true for nearly all species in the Gulf of Alaska and remains an impediment in assessing injury from such catastrophes across most landscapes today. Initial research efforts following the spill focused on damage assessment, including developing methods to accurately estimate the abundance of affected populations and studies of reproduction and survival.
Large scale ecosystem level studies of nearshore species and habitats most affected by the spill completed in 1999, found evidence of long-term spill effects among nearshore species dependent on a nearshore food web where benthic invertebrates transfer primary production to upper level consumers such as sea otters and sea ducks. Biochemical and gene techniques suggested that lingering oil may have contributed to a protracted recovery period for nearshore species. Subsequently, surveys of beaches where oil was deposited nearly a decade earlier found unanticipated volumes of oil sequestered in nearly 20 acres of widely distributed soft sediment intertidal beaches in Prince William Sound.
Our most recent surveys of sea otter abundance indicate significant progress toward recovery, when we consider the entire spill affected area in the Sound. By 2009 our estimate of sea otter abundance in the western Sound was nearly 2,000 animals more than our first post spill estimate in 1993 of about 2,000 individuals. However, when we look only at those areas that were most severely affected by the spill, where sea otter mortality approached 90% and where much of the lingering oil has been located, evidence of recovery remains incomplete. Our most recent research, based on the diving behavior of sea otters in the intertidal and published oil encounter rates, indicates that all sea otters in those heavily oiled areas are likely to encounter Exxon Valdez oil at least annually and some as often as weekly. Long term continuation of studies investigating mortality from the annual collections of beach cast sea otter carcasses implicates elevated mortality as the factor most likely contributing to delayed recovery, and suggests that chronic mortality after the spill may meet or exceed the acute mortality experienced after the spill.
Long-term Monitoring
The Alaska Science Center, and in preceding Department of Interior agencies, has been engaged in monitoring various sea otter populations for more than 50 years, since Karl Kenyon’s seminal work in the Aleutian Islands. As sea otter populations have recovered from the fur trade and translocations contributed to expanding populations, the task of sea otter monitoring has become increasingly difficult simply because of the vast and remote nature of sea otter habitat. Moreover, it has become increasingly evident that monitoring of single species, while perhaps necessary for management purposes, often provides little insight as to why changes in abundance occur over time. As a result we have been engaged in the development, design and testing of monitoring protocols for nearshore habitats and species, including sea otters, that might best be described as “ecosystem” or “food web” based monitoring.
The nearshore is considered an important component of the Gulf of Alaska ecosystem, including the region affected by the Exxon Valdez oil spill, because it provides:
- A variety of unique habitats for resident organisms (e.g. sea otters, harbor seals, shorebirds, seabirds, nearshore fishes, kelps, seagrasses, clams, mussels, and sea stars).
- Nursery grounds for marine animals from other habitats (e.g. crabs, salmon, herring, and seabirds).
- Feeding grounds for important consumers, including killer whales, harbor seals, sea otters, sea lions, sea ducks, shore birds and many fish and shellfish.
- A source of animals important to commercial and subsistence harvests (e.g. marine mammals, fishes, crabs, mussels, clams, chitons, and octopus).
- An important site of recreational activities including fishing, boating, camping, and nature viewing.
- A source of primary production for export to adjacent habitats (primarily by kelps, other seaweeds, and eelgrass), as well as a recipient for primary (phytoplankton) and secondary production (zooplankton) transported from offshore systems..
- An important triple interface between air, land and sea that provides linkages for transfer of water, nutrients, and species between watersheds and offshore habitats.
The underlying assumption in our monitoring design is that change will occur, and that careful consideration of what to monitor, may eventually provide insight as to why observed change occurred. In the nearshore ecosystem we work in, primary productivity is provided by at least two independent sources, the micro-algae, or phytoplankton, that occurs near the sea surface and may be transported inshore via currents. The second, and sometimes major contributor to total primary production is through the kelps and sea grasses that are conspicuous features of the nearshore zone. These combined sources of carbon fuel a diverse community of invertebrates, such as mussels, clams, snails, crustaceans, and urchins, that ultimately transfer their energy to various higher trophic level invertebrates and vertebrates, such as fishes, birds (shore birds, sea ducks and others) and mammals (primarily sea otters). Through careful selection of species and processes (growth, survival and diet) we expect to gain a better understanding of the interaction between various trophic levels that will allow us to potentially assign cause to some of the change we expect to see over time.
As part of the planning efforts of the Exxon Valdez Trustee Council for a long-term science program, in 2001 we were tasked to develop a science and monitoring program for the nearshore ecosystem in the Gulf of Alaska. Through a process of workshops and consultations we developed the Nearshore Restoration and Ecosystem Monitoring program (N-REM, Dean and Bodkin 2006). Coincident with our planning efforts for the Exxon Valdez Trustte Council, the National Park Service was implementing a strategy known as “vital signs monitoring” to develop scientifically sound information on the status and long-term trends of park ecosystems and to determine how well current management practices are sustaining those ecosystems. Subsequently, Park managers from the Southwest Alaska Network (SWAN) recognized that the program we designed for the Exxon Valdez Trustee Council fit their Vital Signs needs and a new partnership was established to implement long term monitoring in the nearshore marine habitat of the SWAN parks.
SWAN consists of five Alaskan park units (Aniakchak National Monument and Preserve, Alagnak National Wild River, Katmai National Park and Preserve, Kenai Fjords National Park, and Lake Clark National Park and Preserve). Collectively these units comprise 9.4 million acres or 11.6 percent of the total land area managed by the National Park Service. Network parks encompass climatic conditions, geologic features, near pristine ecosystems, natural biodiversity, freshwater, and marine resources equaled few places in North America. This network of relatively untouched wilderness parks is a unique resource and offers unparalleled opportunities to study and monitor ecological systems minimally affected by humans. In recognition of this, the SWAN monitoring framework emphasizes (i) establishing reference conditions representing the current status of park, monument, and preserve ecosystems; and (ii) detecting ecological change through time. In 2008, The Exxon Valdez Trustee Council adopted and implemented our nearshore monitoring design in Prince William Sound, extending the SWAN nearshore program from the Gulf of Alaska into Prince William Sound and Kachemak Bay in Cook Inlet. The Gulf of Alaska nearshore monitoring program now consists of four primary sites, including Prince William Sound, Kenai Fjords National Park, Kachemak Bay and Katmai National Park.
- Data
Below are data or web applications associated with this project.
Filter Total Items: 25Morphometric and Reproductive Status Data for Sea Otters Collected or Captured in Alaska
This dataset includes morphometric measurements and pregnancy / dependency status from sea otters captured or collected (experimental harvests or recovered after the Exxon Valdez Oil Spill) in Alaska, 1947-2019 by the U.S. Geological Survey (USGS) and the U.S. Fish and Wildlife Service (USFWS). Data collected include total body length, tail length, body mass, axillary girth, paw width, canine diamSea Otter Aerial Survey Data from Southeast Alaska, 2002-2003
The data package "Sea Otter Aerial Survey Data from Southeast Alaska, 2002-2003" provides raw data for examining abundance and distribution of northern sea otters (Enhydra lutris kenyoni) in Southeast Alaska, based on data collected during a series of population-wide aerial surveys. The USGS aerial sea otter surveys have been completed multiple times using consistent methodology involving aerial-bGulf Watch Alaska Nearshore Component: Sea Otter Aerial Survey Data Katmai National Park and Preserve, 2008 - 2018 (ver 2.0, March 2020)
These data are part of the Gulf Watch Alaska (GWA) long term monitoring program, nearshore monitoring component. Specifically, these data describe sea otter (Enhydra lutris) aerial survey observations from the waters around Katmai National Park and Preserve from surveys conducted in 2008, 2012, 2015, and 2018. Sea otters are a keystone predator, well known for structuring the nearshore marine ecosGulf Watch Alaska, Nearshore Component: Sea Otter Mortality Age Data from Katmai National Park and Preserve, Kenai Fjords National Park, and Prince William Sound, Alaska, 2006-2017
These data are part of the Gulf Watch Alaska (GWA) long term monitoring program, nearshore monitoring component. The dataset is a comma separated file exported from a Microsoft Excel spreadsheet. The data consist of information related to collection of sea otter carcasses. Collectors walked selected shorelines searching for signs of carcasses. Date, location, carcass condition, parts collected, anSea Otter Aerial Survey Data from Glacier Bay National Park and Preserve, 1999-2012
The data package "Sea Otter Aerial Survey Data from Glacier Bay National Park and Preserve, 1999-2012" provides raw data for examining abundance and distribution of northern sea otters (Enhydra lutris kenyoni) in Glacier Bay National Park and Preserve in southeast Alaska, based on data collected during a series of population-wide aerial surveys. The USGS aerial sea otter surveys have been completeIntertidal Soft-Sediment Bivalves from Prince William Sound, Kachemak Bay, Katmai National Park and Preserve, and Kenai Fjords National Park
These data are part of the Gulf Watch Alaska (GWA) long-term monitoring program and describe bivalve count and size sampling and observations conducted at intertidal soft-sediment sampling sites in the northern Gulf of Alaska. This dataset consists of five comma separated files (.csv): 1) bivalve taxonomy table, 2) bivalve sampling site table, 3) bivalve count table, 4) bivalve size table, and 5)Gulf Watch Alaska Nearshore Component: Marine Bird and Mammal Survey Data from Katmai National Park and Preserve and Kenai Fjords National Park, 2012-2016
These data are part of the Gulf Watch Alaska (GWA) long term monitoring program, nearshore monitoring component. The dataset is a series of comma separated files exported from a survey software program (DLog, Ford Consulting, Portland, OR). The data consists of date, time, latitude, longitude, species abbreviation, count, and behavior. Each year the observers attempt to sample the same set of traGulf Watch Alaska Nearshore Component: Sea Otter Aerial Survey Data Kenai Fjords National Park, 2002-2016
These data are is part of the Gulf Watch Alaska (GWA) long term monitoring program, nearshore monitoring component. Specifically, these data describe sea otter (Enhydra lutris) aerial survey observations from the waters around Kenai Fjords National Park between 2002 and 2016. Sea otters are a keystone predator, well known for structuring the nearshore marine ecosystem through their consumption ofSea Otter Gene Transcription Data from Kodiak, the Alaska Peninsula, and Prince William Sound, Alaska, 2005-2012
This data set includes capture location, date, sex, and results of molecular gene transcription analysis for sea otters (Enhydra lutris) sampled in western Prince William Sound (WPWS), Alaska and comparison samples collected from Kodiak and the Alaska Peninsula, and reference samples collected from captive animals. Samples were collected between 2005 and 2012. (Molecular gene transcription is tGulf Watch Alaska, Nearshore Monitoring Component: Sea Otter Foraging Observations from Prince William Sound, Katmai National Park and Preserve, and Kenai Fjords National Park, 2012-2016
This data is part of the Gulf Watch Alaska (GWA) long term monitoring program, benthic monitoring component and a seasonal diet study in Kenai Fjords National Park. The dataset is a comma separated file exported from a Microsoft Access database. The data consists of observations made of foraging sea otters (Enhydra lutris). Observers used Questar field model spotting scopes and binoculars to identBlack Oystercatcher Nest and Diet Data from Kachemak Bay, Katmai National Park and Preserve, Kenai Fjords National Park, and Prince William Sound
These data are part of the Gulf Watch Alaska (GWA) long-term monitoring program, nearshore monitoring component. The dataset is comprised of six comma separated values (.csv) file exported from a relational database. The data consist of: 1) transect summary, 2) nest details, 3) egg float and stage data, 4) chicks diets, 5) chick diet taxonomy, and 6) Gulf Watch Alaska contributors.Gulf Watch Alaska Nearshore Component: Monitoring Site Locations from Prince William Sound, Katmai National Park and Preserve, and Kenai Fjords National Park
These data are part of the Gulf Watch Alaska (GWA) long term monitoring program, nearshore monitoring component. Specifically, these data describe site locations for rocky intertidal, mussel sampling, soft sediment bivalve sampling, and eelgrass bed sampling in the northern Gulf of Alaska within the GWA program. The dataset consists of two comma separated files exported from a Microsoft Excel work - Multimedia
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Filter Total Items: 40Keystone predators govern the pathway and pace of climate impacts in a subarctic marine ecosystem
Predator loss and climate change are hallmarks of the Anthropocene yet their interactive effects are largely unknown. Here, we show that massive calcareous reefs, built slowly by the alga Clathromorphum nereostratum over centuries to millennia, are now declining because of the emerging interplay between these two processes. Such reefs, the structural base of Aleutian kelp forests, are rapidly erodAuthorsDouglas B Rasher, Robert S Stenek, Jochen Halfar, Kristy J Kroeker, Justin B. Ries, M. Tim Tinker, Phoebe T W Chan, J Fietzke, Nicolas Kamenos, Brenda H. Konar, Jonathan S. Lefcheck, Christopher J D Norley, Ben Weitzman, Isaac T Westfield, James A. EstesTrends and carrying capacity of sea otters in Southeast Alaska
Sea otter populations in Southeast Alaska (SEAK) have increased dramatically from fewer than 500 translocated animals in the late 1960s. The recovery of sea otters to ecosystems from which they had been absent has affected coastal food webs, including commercially important fisheries, and thus information on expected growth and equilibrium abundances can help inform resource management. We compileAuthorsM. Tim Tinker, Verena A. Gill, George G. Esslinger, James L. Bodkin, Melissa Monk, Marc Mangel, Daniel Monson, Wendel W. Raymond, Michelle KisslingVariation in abundance of Pacific Blue Mussel (Mytilus trossulus) in the Northern Gulf of Alaska, 2006–2015
Mussels are conspicuous and ecologically important components of nearshore marine communities around the globe. Pacific blue mussels (Mytilus trossulus) are common residents of intertidal habitats in protected waters of the North Pacific, serving as a conduit of primary production to a wide range of nearshore consumers including predatory invertebrates, sea ducks, shorebirds, sea otters, humans, aAuthorsJames L. Bodkin, Heather A. Coletti, Brenda E. Ballachey, Daniel Monson, Daniel Esler, Thomas A. DeanCessation of oil exposure in harlequin ducks after the Exxon Valdez oil spill: Cytochrome P4501A biomarker evidence
The authors quantified hepatic hydrocarbon-inducible cytochrome P4501A (CYP1A) expression, as ethoxyresorufin-O-deethylase (EROD) activity, in wintering harlequin ducks (Histrionicus histrionicus) captured in Prince William Sound, Alaska (USA), during 2011, 2013, and 2014 (22–25 yr following the 1989 Exxon Valdez oil spill). Average EROD activity was compared between birds from areas oiled by theAuthorsDaniel Esler, Brenda E. Ballachey, Lizabeth Bowen, A. Keith Miles, Rian D. Dickson, John D. HendersonWidespread kelp-derived carbon in pelagic and benthic nearshore fishes
Kelp forests provide habitat for diverse and abundant fish assemblages, but the extent to which kelp provides a source of energy to fish and other predators is unclear. To examine the use of kelp-derived energy by fishes we estimated the contribution of kelp- and phytoplankton-derived carbon using carbon (δ13C) and nitrogen (δ15N) isotopes measured in muscle tissue. Benthic-foraging kelp greenlingAuthorsVanessa R. von Biela, Seth D. Newsome, James L. Bodkin, Gordon H. Kruse, Christian E. ZimmermanGene transcript profiling in sea otters post-Exxon Valdez oil spill: A tool for marine ecosystem health assessment
Using a panel of genes stimulated by oil exposure in a laboratory study, we evaluated gene transcription in blood leukocytes sampled from sea otters captured from 2006–2012 in western Prince William Sound (WPWS), Alaska, 17–23 years after the 1989 Exxon Valdez oil spill (EVOS). We compared WPWS sea otters to reference populations (not affected by the EVOS) from the Alaska Peninsula (2009), KatmaiAuthorsLizabeth Bowen, A. Keith Miles, Brenda E. Ballachey, Shannon C. Waters, James L. BodkinInfluence of basin- and local-scale environmental conditions on nearshore production in the northeast Pacific Ocean
Nearshore marine habitats are productive and vulnerable owing to their connections to pelagic and terrestrial landscapes. To understand how ocean basin- and local-scale conditions may influence nearshore species, we developed an annual index of nearshore production (spanning the period 1972–2010) from growth increments recorded in otoliths of representative pelagic-feeding (Black Rockfish SebastesAuthorsVanessa R. von Biela, Christian E. Zimmerman, Gordon H. Kruse, Franz J. Mueter, Bryan A. Black, David C. Douglas, James L. BodkinInfluence of static habitat attributes on local and regional Rocky intertidal community structure
Rocky intertidal communities are structured by local environmental drivers, which can be dynamic, fluctuating on various temporal scales, or static and not greatly varying across years. We examined the role of six static drivers (distance to freshwater, tidewater glacial presence, wave exposure, fetch, beach slope, and substrate composition) on intertidal community structure across the northern GuAuthorsB. Konar, K. Iken, H. Coletti, Daniel H. Monson, Ben P. WeitzmanMonitoring population status of sea otters (Enhydra lutris) in Glacier Bay National Park and Preserve, Alaska: options and considerations
After many decades of absence from southeast Alaska, sea otters (Enhydra lutris) are recolonizing parts of their former range, including Glacier Bay, Alaska. Sea otters are well known for structuring nearshore ecosystems and causing community-level changes such as increases in kelp abundance and changes in the size and number of other consumers. Monitoring population status of sea otters in GlacieAuthorsGeorge G. Esslinger, Daniel Esler, S. Howlin, L.A. StarcevichThe interaction of intraspecific competition and habitat on individual diet specialization: a near range-wide examination of sea otters
The quantification of individuality is a common research theme in the fields of population, community, and evolutionary ecology. The potential for individuality to arise is likely context-dependent, and the influence of habitat characteristics on its prevalence has received less attention than intraspecific competition. We examined individual diet specialization in 16 sea otter (Enhydra lutris) poAuthorsSeth D. Newsome, M. Tim Tinker, Verena A. Gill, Zachary N. Hoyt, Angela M. Doroff, Linda Nichol, James L. BodkinEvaluating the status of individuals and populations: Advantages of multiple approaches and time scales
The assessment of population status is a central goal of applied wildlife research and essential to the field of wildlife conservation. “Population status” has a number of definitions, the most widely used having to do with the current trajectory of the population (i.e., growing, stable, or declining), or the probability of persistence (i.e., extinction risk), perhaps without any specific knowledgAuthorsDaniel H. Monson, Lizabeth BowenTimelines and mechanisms of wildlife population recovery following the Exxon Valdez Oil Spill
In March 1989, the T/V Exxon Valdez ran aground in Prince William Sound (PWS), Alaska and spilled an estimated 42 million liters of crude oil (Wolfe et al. 1994). This oil subsequently spread over more than 26,000 km2 of water surface in PWS and the Gulf of Alaska and landed on more than 1000 km of shoreline (Spies et al. 1996, Short et al. 2004; see Fig. 1 in Esler et al., this report). Initial cAuthorsDaniel Esler, James L. Bodkin, Brenda E. Ballachey, Daniel Monson, Kimberly A. Kloecker, George G. Esslinger - News
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