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.
North Pacific Wintering Barrow's Goldeneye Body Mass, Morphology, and Prey Sizes 1996-2015
Rocky Intertidal Data from Prince William Sound, Katmai National Park and Preserve, and Kenai Fjords National Park
Intertidal Temperature Data from Kachemak Bay, Prince William Sound, Katmai National Park and Preserve, and Kenai Fjords National Park
Sea Otter Spraint Data from Kachemak Bay, Katmai National Park and Preserve, Kenai Fjords National Park and Prince William Sound
Intertidal Mussel (Mytilus) Data from Prince William Sound, Katmai National Park and Preserve, and Kenai Fjords National Park
Intertidal and Subtidal Sea Otter Prey Sampling in Mixed Sediment Habitat in Glacier Bay National Park and Preserve, Alaska, 1998 to 2011
Sea Otter Aerial Survey Data from Lower Cook Inlet, Alaska, 2017
Sea Otter Aerial Survey Data from Western Prince William Sound, Alaska, 2017
Sea Otter Aerial Survey Data from the outer Kenai Peninsula, Alaska, 2019
Sea Otter Aerial Survey Data from Northern and Eastern Prince William Sound, Alaska, 2014
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)
Below are publications associated with this project.
Brown bear–sea otter interactions along the Katmai coast: Terrestrial and nearshore communities linked by predation
Where land and sea meet: Brown bears and sea otters
Abundance and distribution of sea otters (Enhydra lutris) in the southcentral Alaska stock, 2014, 2017, and 2019
Diffusion modeling reveals effects of multiple release sites and human activity on a recolonizing apex predator
Translocations maintain genetic diversity and increase connectivity in sea otters, Enhydra lutris
Sea otter predator avoidance behavior
Biological correlates of sea urchin recruitment in kelp forest and urchin barren habitats
Changes in rocky intertidal community structure during a marine heatwave in the northern Gulf of Alaska
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
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: 14North Pacific Wintering Barrow's Goldeneye Body Mass, Morphology, and Prey Sizes 1996-2015
These data provide information in support of the creation of a bioenergetic model to estimate winter prey consumption by Barrow's Goldeneye (Bucephala islandica). One table consists of mass and morphological measurements of wintering Barrows Goldeneyes captured or collected in Alaska and British Columbia from 1996 to 2015. The second table consists of size classes of Pacific blue mussels (MytilusRocky Intertidal Data 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. The dataset consists of 10 tables of data organized into four folders. The data are presented in Comma Separated Value (CSV) format exported from a Microsoft Access relational database. The tables are: 1) invertebrate taxonomy, 2) limpet size, 3) limpet counts, 4) Nucella, Katharina, anIntertidal Temperature Data from Kachemak Bay, 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. This dataset consists of date, time, and temperature measurements from intertidal rocky sampling sites, including predicted tide height at the time of the reading, which is used to distinguish air from water temperature readings. The data are provided as comma separated values (.csv) files derived from data downloadedSea Otter Spraint 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. This dataset consist of observations of sea otter (Enhydra lutris) fecal samples (spraint). Observers examined fresh spraint piles to identify major prey classes in the samples and to determine sea otter diets in the Gulf of Alaska region.Intertidal Mussel (Mytilus) Data 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 and describe mussel sampling and observations conducted in the northern Gulf of Alaska. This dataset consists of six comma separated files (.csv): 1) mussel sampling site layout information, 2) mussel counts for mussels greater than 20 millimeters in a quadrat, 3) mussel size measurements for mussels greater than 20 miIntertidal and Subtidal Sea Otter Prey Sampling in Mixed Sediment Habitat in Glacier Bay National Park and Preserve, Alaska, 1998 to 2011
This dataset provides clam species abundance and size data from intertidal and subtidal mixed sediment habitats in Glacier Bay National Park and Preserve (GBNPP). Data are provided for all observed clams, horse mussels, or urchins 14 mm or larger. Sampling involved excavating 25 cm of substrate from quadrats (approximately 0.25 sq meter) along transects at random and selected sites, 10 quadrats atSea Otter Aerial Survey Data from Lower Cook Inlet, Alaska, 2017
This dataset consists of three tables related to abundance and distribution of northern sea otters (Enhydra lutris kenyoni) in lower Cook Inlet, Alaska, based on data collected during a series of population-wide aerial surveys in May 2017. The dataset consists of: (1) sea otter counts along strip transects, (2) sea otter counts in Intensive Search Unit (ISU) within the transects, and (3) TransectSea Otter Aerial Survey Data from Western Prince William Sound, Alaska, 2017
This dataset consists of three tables related to abundance and distribution of northern sea otters (Enhydra lutris kenyoni) in western Prince William Sound, Alaska, based on data collected during a series of population-wide aerial surveys in June 2017. The dataset consists of: (1) sea otter counts along strip transects, (2) sea otter counts in Intensive Search Unit (ISU) within the transects, andSea Otter Aerial Survey Data from the outer Kenai Peninsula, Alaska, 2019
This dataset consists of three tables related to abundance and distribution of northern sea otters (Enhydra lutris kenyoni) near the outer Kenai Peninsula, Alaska, based on data collected during a series of population-wide aerial surveys in June 2019. The dataset consists of: (1) sea otter counts along strip transects, (2) sea otter counts in Intensive Search Unit (ISU) within the transects, and (Sea Otter Aerial Survey Data from Northern and Eastern Prince William Sound, Alaska, 2014
This dataset consists of three tables related to abundance and distribution of northern sea otters (Enhydra lutris kenyoni) in northern and eastern Prince William Sound, Alaska, based on data collected during a series of population-wide aerial surveys in June 2014. The dataset consists of: (1) sea otter counts along strip transects, (2) sea otter counts in Intensive Search Unit (ISU) within the trSea 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 involvinGulf 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 ecos - Multimedia
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Below are publications associated with this project.
Filter Total Items: 36Brown bear–sea otter interactions along the Katmai coast: Terrestrial and nearshore communities linked by predation
Sea otters were extirpated throughout much of their range by the maritime fur trade in the 18th and 19th centuries, including the coast of Katmai National Park and Preserve in southcentral Alaska. Brown bears are an important component of the Katmai ecosystem where they are the focus of a thriving ecotourism bear-viewing industry as they forage in sedge meadows and dig clams in the extensive tidalWhere land and sea meet: Brown bears and sea otters
In Katmai National Park, Alaska, USA, we have seen changes in the number of brown bears and sea otters. The number of animals of a species a habitat can support is called carrying capacity. Even though bears live on land and sea otters live in the ocean, these two mammals share coastal habitats. Bears eat salmon, other fish, plants, clams, and beached whales. Sea otters feed on clams and other marAbundance and distribution of sea otters (Enhydra lutris) in the southcentral Alaska stock, 2014, 2017, and 2019
The Southcentral Alaska (SCAK) sea otter (Enhydra lutris) stock is the northernmost stock of sea otters, a keystone predator known for structuring nearshore marine ecosystems. We conducted aerial surveys within the range of the SCAK sea otter stock to provide recent estimates of sea otter abundance and distribution. We defined three survey regions: (1) Eastern Cook Inlet (2017), (2) Outer Kenai PeDiffusion modeling reveals effects of multiple release sites and human activity on a recolonizing apex predator
BackgroundReintroducing predators is a promising conservation tool to help remedy human-caused ecosystem changes. However, the growth and spread of a reintroduced population is a spatiotemporal process that is driven by a suite of factors, such as habitat change, human activity, and prey availability. Sea otters (Enhydra lutris) are apex predators of nearshore marine ecosystems that had declined nTranslocations maintain genetic diversity and increase connectivity in sea otters, Enhydra lutris
Sea otters, Enhydra lutris, were once abundant along the nearshore areas of the North Pacific. The international maritime fur trade that ended in 1911 left 13 small remnant populations with low genetic diversity. Subsequent translocations into previously occupied habitat resulted in several reintroduced populations along the coast of North America. We sampled sea otters between 2008 and 2011 throuSea otter predator avoidance behavior
Predators directly affect their prey as a source of mortality, and prey respond by employing antipredator strategies. Sea otters are a keystone predator within the nearshore community, but higher trophic level avian, terrestrial, and pelagic predators (e.g., bald eagles, brown bears, wolves, white sharks, and killer whales) prey on them. Three antipredator strategies used by sea otters are vigilanBiological correlates of sea urchin recruitment in kelp forest and urchin barren habitats
Shifts between the alternate stable states of sea urchin barren grounds and kelp forests correspond to sea urchin density. In the Aleutian Archipelago, green sea urchins Strongylocentrotus polyacanthus are the dominant herbivores that graze kelp forests. Sea urchin recruitment is an important driver that influences sea urchin density, particularly in the absence of top-down control from a keystoneChanges in rocky intertidal community structure during a marine heatwave in the northern Gulf of Alaska
Marine heatwaves are global phenomena that can have major impacts on the structure and function of coastal ecosystems. By mid-2014, the Pacific Marine Heatwave (PMH) was evident in intertidal waters of the northern Gulf of Alaska and persisted for multiple years. While offshore marine ecosystems are known to respond to these warmer waters, the response of rocky intertidal ecosystems to this warminKeystone 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 erodTrends 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 compileVariation 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, aCessation 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 the - News
Below are news stories associated with this project.