Many organohalogen compounds (OHCs) are persistent organic pollutants (POPs) found in appreciable... more Many organohalogen compounds (OHCs) are persistent organic pollutants (POPs) found in appreciable concentrations in marine predators. While production of some POPs has declined or ceased in recent decades, their capacity for global transport and bioaccumulation results in observations of unchanging or increasing concentrations in marine systems. Sea otters (Enhydra lutris) have been advocated as an environmental sentinel for contaminants due to their longevity, site fidelity and prey species that often overlap with human consumption. Using archived (1992-2010) samples of livers from Northern sea otters (n=50) from Alaska we examine concentrations of chlordanes (CHLs), polychlorinated biphenyls (PCBs) dichlorodiphenyltrichloroethane (DDTs), and polybrominated diphenyl ethers (PBDEs) and associated metabolites. We found some evidence for declining ΣPCBs over the two decades, however for most animals concentrations were low compared to toxicological thresholds. Six animals had relatively high concentrations of ΣPCBs (mean=262,000 ng/g lipid weight), ΣDDTs (mean=8800 ng/g lw), and ΣPBDEs (mean=4,600 ng/g lw), with four of these six animals experiencing hepatic parasitism or hepatitis. In order to assess whether differences in POPs concentrations are associated with feeding ecology, we examined stable isotopes of C and N in archived muscle and whisker samples. In general, there were no significant relationships between ΣPOP concentrations and stable isotope ratios. There were small differences in stable isotope profiles in animals with high POP concentrations, although it was unclear if these differences were due to feeding ecology or disease processes. This study highlights the importance of considering feeding ecology and necropsy (health and disease status) data while conducting contaminant surveys, and confirms some previous reports of trends in OHCs in Alaska marine mammals.
For the sea otter (Enhydra lutris), genetic population structure is an area of research that has ... more For the sea otter (Enhydra lutris), genetic population structure is an area of research that has not received significant attention, especially in Southwest Alaska where that distinct population segment has been listed as threatened since 2005 pursuant to the U.S. Endangered Species Act. In this study, 501 samples from 14 locations from Prince William Sound, Alaska to the Commander Islands in Russia were analyzed for variation at 13 microsatellite loci. Our results indicate a high degree of genetic divergence among the 14 locations (FST = 0.120) with gene flow conforming to the isolation by distance (IBD) model (r2 = 0.491, p < .05). The 14 sampling locations formed six geographic associations in clustering and ordination analyses that likely correspond to remnant population lineages: (1) Southcentral Alaska, (2) Kodiak and North Alaska Peninsula, (3) South Alaska Peninsula and Bristol Bay, (4) Eastern Aleutian, (5) Western Aleutian, and (6) the Commander Islands. Except for South Alaska Peninsula and Bristol Bay, these clusters closely agree with previously defined stock and management unit boundaries. Our results reveal significant genetic population structure and are generally congruent with current management strategies for the threatened Southwest Alaska distinct population segment.
BackgroundIn the North Pacific, northern fulmar (Fulmarus glacialis) forms extensive colonies in ... more BackgroundIn the North Pacific, northern fulmar (Fulmarus glacialis) forms extensive colonies in few locales, which may lead to limited gene flow and locale-specific population threats. In the Atlantic, there are thousands of colonies of varying sizes and in Europe the species is considered threatened. Prior screens and classical microsatellite development in fulmar failed to provide a suite of markers adequate for population genetics studies.ObjectivesThe objective of this study was to isolate a suite of polymorphic microsatellite loci with sufficient variability to quantify levels of gene flow, population affinity, and identify familial relationships in fulmar. We also performed a cross-species screening of these markers in eight other species.MethodsWe used shotgun sequencing to isolate 26 novel microsatellite markers in fulmar to screen for variability using individuals from two distinct regions: the Pacific (Chagulak Island, Alaska) and the Atlantic (Hafnarey Island, Iceland).ResultsPolymorphism was present in 24 loci in Chagulak and 23 in Hafnarey, while one locus failed to amplify in either colony. Polymorphic loci exhibited moderate levels of genetic diversity and this suite of loci uncovered genetic structuring between the regions. Among the other species screened, polymorphism was present in one to seven loci.ConclusionThe loci yielded sufficient variability for use in population studies and estimation of familial relationships; as few as five loci provide resolution to determine individual identity. These markers will allow further insight into the global population dynamics and phylogeography of fulmars. We also demonstrated some markers are transferable to other species.
Climate change-driven alterations in Arctic environments can influence habitat availability, spec... more Climate change-driven alterations in Arctic environments can influence habitat availability, species distributions and interactions, and the breeding, foraging, and health of marine mammals. Phocine distemper virus (PDV), which has caused extensive mortality in Atlantic seals, was confirmed in sea otters in the North Pacific Ocean in 2004, raising the question of whether reductions in sea ice could increase contact between Arctic and sub-Arctic marine mammals and lead to viral transmission across the Arctic Ocean. Using data on PDV exposure and infection and animal movement in sympatric seal, sea lion, and sea otter species sampled in the North Pacific Ocean from 2001–2016, we investigated the timing of PDV introduction, risk factors associated with PDV emergence, and patterns of transmission following introduction. We identified widespread exposure to and infection with PDV across the North Pacific Ocean beginning in 2003 with a second peak of PDV exposure and infection in 2009; vi...
Journal of Experimental Marine Biology and Ecology, 2016
Lactation is a critical and energetically expensive period of reproduction, especially for female... more Lactation is a critical and energetically expensive period of reproduction, especially for female sea otters (Enhydra lutris) and their pups, both of which have resting metabolic rates that are ca. 2.5-fold higher than terrestrial mammals of similar size. The simultaneous energy budgets for female Alaskan sea otters and their pups during the first three months postpartum were calculated based on published activity budgets for wild animals and metabolic rates for specific behaviors of captive sea otters. Pups were classified into three behavioral/size categories: Category 1 (C1) 0–b4 wk. old; Category 2 (C2) 4–b8 wk. old; and Category 3 (C3) 8–12 wk. Energy for growth (Energy growth) averaged 0.0416 MJ day −1 for all pups. The combined daily energy expenditure to support resting metabolism and activity (Energy r + a) for C1 and C2 pups was 1.31 and 2.61 MJ day −1 , respectively, of which most (C1: 99%; C2: 84%) was associated with resting-equivalent behaviors (i.e., resting, nursing and being groomed by the female). Energy r + a for C3 pups was 4.62 MJ day −1 of which 49% was associated with resting-equivalent behaviors, while 35% was associated with active behaviors (i.e., feeding, swimming and grooming). The underlying resting metabolic rate for all behaviors represented 100% of Energy ingest for C1, 94% for C2 and 85% for C3 pups. Energy r + a for all females was similar regardless of pup age and averaged 10.88 MJ day −1 (range 10.79–11.03). Energy r + a for C1 females was associated mainly with self-grooming and pup grooming (30%) and swimming (25%), while only 10% was associated with feeding. Energy r + a for C3 females was mainly associated with feeding (37%) with less energy devoted to swimming (10%) and grooming (14%). Lactation energy (Energy lactation) in C3 females was 3.5-fold greater than in C1 females. Ingested energy for C1 females was 19.55 MJ day −1 , which increased to 22.13 MJ day −1 for C2 females and 26.53 MJ day −1 for C3 females. As with pups, the underlying resting metabolic rate for all female behaviors represented 70% of Energy ingest for C1 females and 72% for C2 and C3 females. Hence, thermogenesis dominated the metabolism of female sea otters as with their pups. These results provide a quantitative picture of the energetics of Alaskan female sea otters and their pups during early pup rearing in a species that has one of the highest mass specific resting metabolic rates of any mammal and the most altricial neonate born at sea.
Journal of Experimental Marine Biology and Ecology, 2016
Lactation is a critical and energetically expensive period of reproduction, especially for female... more Lactation is a critical and energetically expensive period of reproduction, especially for female sea otters (Enhydra lutris) and their pups, both of which have resting metabolic rates that are ca. 2.5-fold higher than terrestrial mammals of similar size. The simultaneous energy budgets for female Alaskan sea otters and their pups during the first three months postpartum were calculated based on published activity budgets for wild animals and metabolic rates for specific behaviors of captive sea otters. Pups were classified into three behavioral/size categories: Category 1 (C1) 0–b4 wk. old; Category 2 (C2) 4–b8 wk. old; and Category 3 (C3) 8–12 wk. Energy for growth (Energy growth) averaged 0.0416 MJ day −1 for all pups. The combined daily energy expenditure to support resting metabolism and activity (Energy r + a) for C1 and C2 pups was 1.31 and 2.61 MJ day −1 , respectively, of which most (C1: 99%; C2: 84%) was associated with resting-equivalent behaviors (i.e., resting, nursing and being groomed by the female). Energy r + a for C3 pups was 4.62 MJ day −1 of which 49% was associated with resting-equivalent behaviors, while 35% was associated with active behaviors (i.e., feeding, swimming and grooming). The underlying resting metabolic rate for all behaviors represented 100% of Energy ingest for C1, 94% for C2 and 85% for C3 pups. Energy r + a for all females was similar regardless of pup age and averaged 10.88 MJ day −1 (range 10.79–11.03). Energy r + a for C1 females was associated mainly with self-grooming and pup grooming (30%) and swimming (25%), while only 10% was associated with feeding. Energy r + a for C3 females was mainly associated with feeding (37%) with less energy devoted to swimming (10%) and grooming (14%). Lactation energy (Energy lactation) in C3 females was 3.5-fold greater than in C1 females. Ingested energy for C1 females was 19.55 MJ day −1 , which increased to 22.13 MJ day −1 for C2 females and 26.53 MJ day −1 for C3 females. As with pups, the underlying resting metabolic rate for all female behaviors represented 70% of Energy ingest for C1 females and 72% for C2 and C3 females. Hence, thermogenesis dominated the metabolism of female sea otters as with their pups. These results provide a quantitative picture of the energetics of Alaskan female sea otters and their pups during early pup rearing in a species that has one of the highest mass specific resting metabolic rates of any mammal and the most altricial neonate born at sea.
ABSTRACT Background/Question/Methods The recognition and quantification of individuality is now a... more ABSTRACT Background/Question/Methods The recognition and quantification of individuality is now a common research theme in the fields of behavioral, evolutionary, community, and population ecology. Individual level differences in behavior, prey choice, and movement have been documented over a wide variety of taxa and ecosystems. The potential for individuality in a population is likely context dependent, and the influence of habitat characteristics, which can be strongly correlated with (prey) diversity, on the prevalence of individuality has received less attention than competition. We examined individual diet specialization in ~15 sea otter (Enhydra lutris) populations across the entire northeast Pacific margin from southern California to the central Aleutian Islands, Alaska. Because exploitation/management histories and general habitat characteristics vary among these sites, we could examine the effects of prey diversity/availability and intra-specific competition on the prevalence of individual diet specialization. We used observational dietary data to quantify prey diversity and characterize relative habitat availability. We primarily relied on stable isotope data to quantify population and individual dietary variation and individuality. As in previous isotope-based studies of individuality, we defined the within-individual component (WIC) as the amount of intra-individual isotopic variation and the total isotopic niche width as the sum of the WIC and between-individual components (BIC). Results/Conclusions Using observational diet data, we classified half of our sites as rocky-substrate habitats, while the others contained a mixture of rocky substrate and soft-sediment habitats. Previous studies have shown that in rocky substrate habitats in California, individuality increases with intra-specific competition as measured by sea otter density. Our results, which include data for 8 rocky substrate sites from southern California to the central Aleutians, support previous findings. Specifically, the slope of the relationship between the within-individual component (WIC) and total isotopic niche width (TINW) was low (0.24) but significant (P<0.001, R2=0.90). Furthermore, population dietary diversity (TINW) was positively correlated with sea otter density. In contrast, the slope of the significant relationship (P<0.001, R2=0.95) between WIC and TINW for otter populations inhabiting mixed substrate sites was much higher (0.50), suggesting a low degree of individuality irrespective of competition (i.e., sea otter density). Our results show that the potential for individuality to occur as a result of increasing intra-specific competition is context dependent and that habitat characteristics, which ultimately influence prey diversity and abundance, are important in determining when and where individual specialization occurs in nature.
Archives of Environmental Contamination and Toxicology, 2009
Perfluorinated chemicals (PFCs) have been detected in abiotic and biotic matrices worldwide, incl... more Perfluorinated chemicals (PFCs) have been detected in abiotic and biotic matrices worldwide, including the Arctic Ocean. Considering these chemicals' persistent and bioaccumulative potentials, it was expected that levels of PFCs, like those of many legacy organic pollutants, would respond slowly to the restrictions in production and usage. Temporal trend studies in remote areas, such as the Arctic, can help determine the chronology of contamination and the response of the environment to regulations on PFCs. Prior to this study, temporal trends of PFCs in Alaskan coastal waters had not been examined. In the present study, concentrations of six PFCs were determined in livers of northern sea otters (Enhydra lutris kenyoni) collected from three areas in south-central Alaska (Prince William Sound, n = 36; Resurrection Bay, n = 7; Kachemak Bay, n = 34) from 1992 to 2007. Additionally, previously published profiles and concentrations of PFCs in southern sea otters from California and Asian sea otters from Kamchatka (Russia) were compared to our new data, to determine the geographical differences in PFC profiles among these three regions in the Pacific Ocean. Perfluorooctanesulfonate (PFOS), perfluorooctanesulfonamide (PFOSA), and perfluorononanoate (PFNA) were the predominant PFCs found in the livers of northern sea otters from 1992 to 2007. Other PFCs, such as perfluorooctanoate (PFOA), perfluoroundecanoate (PFUnDA), and perfluorodecanoate (PFDA), were detected less frequently, and at low concentrations. Overall, from 2001 to 2007, a decrease in concentrations of PFOS was found in northern sea otters, suggesting an immediate response to the phase-out in 2000 of perfluorooctanesulfonyl-based compounds by a major producer in the United States. In contrast, concentrations of PFNA in northern sea otters increased by 10-fold from 2004 to 2007. These results indicate that the contribution by PFNA to SigmaPFC concentrations is increasing in northern sea otters. The profiles (i.e., composition of individual PFC to SigmaPFC concentration) of PFCs in northern sea otters from Alaska were similar to those reported for southern sea otters from California, but were considerably different from the profiles reported for Asian sea otters from Russia, suggesting differences in point sources of exposure.
Many organohalogen compounds (OHCs) are persistent organic pollutants (POPs) found in appreciable... more Many organohalogen compounds (OHCs) are persistent organic pollutants (POPs) found in appreciable concentrations in marine predators. While production of some POPs has declined or ceased in recent decades, their capacity for global transport and bioaccumulation results in observations of unchanging or increasing concentrations in marine systems. Sea otters (Enhydra lutris) have been advocated as an environmental sentinel for contaminants due to their longevity, site fidelity and prey species that often overlap with human consumption. Using archived (1992-2010) samples of livers from Northern sea otters (n=50) from Alaska we examine concentrations of chlordanes (CHLs), polychlorinated biphenyls (PCBs) dichlorodiphenyltrichloroethane (DDTs), and polybrominated diphenyl ethers (PBDEs) and associated metabolites. We found some evidence for declining ΣPCBs over the two decades, however for most animals concentrations were low compared to toxicological thresholds. Six animals had relatively high concentrations of ΣPCBs (mean=262,000 ng/g lipid weight), ΣDDTs (mean=8800 ng/g lw), and ΣPBDEs (mean=4,600 ng/g lw), with four of these six animals experiencing hepatic parasitism or hepatitis. In order to assess whether differences in POPs concentrations are associated with feeding ecology, we examined stable isotopes of C and N in archived muscle and whisker samples. In general, there were no significant relationships between ΣPOP concentrations and stable isotope ratios. There were small differences in stable isotope profiles in animals with high POP concentrations, although it was unclear if these differences were due to feeding ecology or disease processes. This study highlights the importance of considering feeding ecology and necropsy (health and disease status) data while conducting contaminant surveys, and confirms some previous reports of trends in OHCs in Alaska marine mammals.
For the sea otter (Enhydra lutris), genetic population structure is an area of research that has ... more For the sea otter (Enhydra lutris), genetic population structure is an area of research that has not received significant attention, especially in Southwest Alaska where that distinct population segment has been listed as threatened since 2005 pursuant to the U.S. Endangered Species Act. In this study, 501 samples from 14 locations from Prince William Sound, Alaska to the Commander Islands in Russia were analyzed for variation at 13 microsatellite loci. Our results indicate a high degree of genetic divergence among the 14 locations (FST = 0.120) with gene flow conforming to the isolation by distance (IBD) model (r2 = 0.491, p < .05). The 14 sampling locations formed six geographic associations in clustering and ordination analyses that likely correspond to remnant population lineages: (1) Southcentral Alaska, (2) Kodiak and North Alaska Peninsula, (3) South Alaska Peninsula and Bristol Bay, (4) Eastern Aleutian, (5) Western Aleutian, and (6) the Commander Islands. Except for South Alaska Peninsula and Bristol Bay, these clusters closely agree with previously defined stock and management unit boundaries. Our results reveal significant genetic population structure and are generally congruent with current management strategies for the threatened Southwest Alaska distinct population segment.
BackgroundIn the North Pacific, northern fulmar (Fulmarus glacialis) forms extensive colonies in ... more BackgroundIn the North Pacific, northern fulmar (Fulmarus glacialis) forms extensive colonies in few locales, which may lead to limited gene flow and locale-specific population threats. In the Atlantic, there are thousands of colonies of varying sizes and in Europe the species is considered threatened. Prior screens and classical microsatellite development in fulmar failed to provide a suite of markers adequate for population genetics studies.ObjectivesThe objective of this study was to isolate a suite of polymorphic microsatellite loci with sufficient variability to quantify levels of gene flow, population affinity, and identify familial relationships in fulmar. We also performed a cross-species screening of these markers in eight other species.MethodsWe used shotgun sequencing to isolate 26 novel microsatellite markers in fulmar to screen for variability using individuals from two distinct regions: the Pacific (Chagulak Island, Alaska) and the Atlantic (Hafnarey Island, Iceland).ResultsPolymorphism was present in 24 loci in Chagulak and 23 in Hafnarey, while one locus failed to amplify in either colony. Polymorphic loci exhibited moderate levels of genetic diversity and this suite of loci uncovered genetic structuring between the regions. Among the other species screened, polymorphism was present in one to seven loci.ConclusionThe loci yielded sufficient variability for use in population studies and estimation of familial relationships; as few as five loci provide resolution to determine individual identity. These markers will allow further insight into the global population dynamics and phylogeography of fulmars. We also demonstrated some markers are transferable to other species.
Climate change-driven alterations in Arctic environments can influence habitat availability, spec... more Climate change-driven alterations in Arctic environments can influence habitat availability, species distributions and interactions, and the breeding, foraging, and health of marine mammals. Phocine distemper virus (PDV), which has caused extensive mortality in Atlantic seals, was confirmed in sea otters in the North Pacific Ocean in 2004, raising the question of whether reductions in sea ice could increase contact between Arctic and sub-Arctic marine mammals and lead to viral transmission across the Arctic Ocean. Using data on PDV exposure and infection and animal movement in sympatric seal, sea lion, and sea otter species sampled in the North Pacific Ocean from 2001–2016, we investigated the timing of PDV introduction, risk factors associated with PDV emergence, and patterns of transmission following introduction. We identified widespread exposure to and infection with PDV across the North Pacific Ocean beginning in 2003 with a second peak of PDV exposure and infection in 2009; vi...
Journal of Experimental Marine Biology and Ecology, 2016
Lactation is a critical and energetically expensive period of reproduction, especially for female... more Lactation is a critical and energetically expensive period of reproduction, especially for female sea otters (Enhydra lutris) and their pups, both of which have resting metabolic rates that are ca. 2.5-fold higher than terrestrial mammals of similar size. The simultaneous energy budgets for female Alaskan sea otters and their pups during the first three months postpartum were calculated based on published activity budgets for wild animals and metabolic rates for specific behaviors of captive sea otters. Pups were classified into three behavioral/size categories: Category 1 (C1) 0–b4 wk. old; Category 2 (C2) 4–b8 wk. old; and Category 3 (C3) 8–12 wk. Energy for growth (Energy growth) averaged 0.0416 MJ day −1 for all pups. The combined daily energy expenditure to support resting metabolism and activity (Energy r + a) for C1 and C2 pups was 1.31 and 2.61 MJ day −1 , respectively, of which most (C1: 99%; C2: 84%) was associated with resting-equivalent behaviors (i.e., resting, nursing and being groomed by the female). Energy r + a for C3 pups was 4.62 MJ day −1 of which 49% was associated with resting-equivalent behaviors, while 35% was associated with active behaviors (i.e., feeding, swimming and grooming). The underlying resting metabolic rate for all behaviors represented 100% of Energy ingest for C1, 94% for C2 and 85% for C3 pups. Energy r + a for all females was similar regardless of pup age and averaged 10.88 MJ day −1 (range 10.79–11.03). Energy r + a for C1 females was associated mainly with self-grooming and pup grooming (30%) and swimming (25%), while only 10% was associated with feeding. Energy r + a for C3 females was mainly associated with feeding (37%) with less energy devoted to swimming (10%) and grooming (14%). Lactation energy (Energy lactation) in C3 females was 3.5-fold greater than in C1 females. Ingested energy for C1 females was 19.55 MJ day −1 , which increased to 22.13 MJ day −1 for C2 females and 26.53 MJ day −1 for C3 females. As with pups, the underlying resting metabolic rate for all female behaviors represented 70% of Energy ingest for C1 females and 72% for C2 and C3 females. Hence, thermogenesis dominated the metabolism of female sea otters as with their pups. These results provide a quantitative picture of the energetics of Alaskan female sea otters and their pups during early pup rearing in a species that has one of the highest mass specific resting metabolic rates of any mammal and the most altricial neonate born at sea.
Journal of Experimental Marine Biology and Ecology, 2016
Lactation is a critical and energetically expensive period of reproduction, especially for female... more Lactation is a critical and energetically expensive period of reproduction, especially for female sea otters (Enhydra lutris) and their pups, both of which have resting metabolic rates that are ca. 2.5-fold higher than terrestrial mammals of similar size. The simultaneous energy budgets for female Alaskan sea otters and their pups during the first three months postpartum were calculated based on published activity budgets for wild animals and metabolic rates for specific behaviors of captive sea otters. Pups were classified into three behavioral/size categories: Category 1 (C1) 0–b4 wk. old; Category 2 (C2) 4–b8 wk. old; and Category 3 (C3) 8–12 wk. Energy for growth (Energy growth) averaged 0.0416 MJ day −1 for all pups. The combined daily energy expenditure to support resting metabolism and activity (Energy r + a) for C1 and C2 pups was 1.31 and 2.61 MJ day −1 , respectively, of which most (C1: 99%; C2: 84%) was associated with resting-equivalent behaviors (i.e., resting, nursing and being groomed by the female). Energy r + a for C3 pups was 4.62 MJ day −1 of which 49% was associated with resting-equivalent behaviors, while 35% was associated with active behaviors (i.e., feeding, swimming and grooming). The underlying resting metabolic rate for all behaviors represented 100% of Energy ingest for C1, 94% for C2 and 85% for C3 pups. Energy r + a for all females was similar regardless of pup age and averaged 10.88 MJ day −1 (range 10.79–11.03). Energy r + a for C1 females was associated mainly with self-grooming and pup grooming (30%) and swimming (25%), while only 10% was associated with feeding. Energy r + a for C3 females was mainly associated with feeding (37%) with less energy devoted to swimming (10%) and grooming (14%). Lactation energy (Energy lactation) in C3 females was 3.5-fold greater than in C1 females. Ingested energy for C1 females was 19.55 MJ day −1 , which increased to 22.13 MJ day −1 for C2 females and 26.53 MJ day −1 for C3 females. As with pups, the underlying resting metabolic rate for all female behaviors represented 70% of Energy ingest for C1 females and 72% for C2 and C3 females. Hence, thermogenesis dominated the metabolism of female sea otters as with their pups. These results provide a quantitative picture of the energetics of Alaskan female sea otters and their pups during early pup rearing in a species that has one of the highest mass specific resting metabolic rates of any mammal and the most altricial neonate born at sea.
ABSTRACT Background/Question/Methods The recognition and quantification of individuality is now a... more ABSTRACT Background/Question/Methods The recognition and quantification of individuality is now a common research theme in the fields of behavioral, evolutionary, community, and population ecology. Individual level differences in behavior, prey choice, and movement have been documented over a wide variety of taxa and ecosystems. The potential for individuality in a population is likely context dependent, and the influence of habitat characteristics, which can be strongly correlated with (prey) diversity, on the prevalence of individuality has received less attention than competition. We examined individual diet specialization in ~15 sea otter (Enhydra lutris) populations across the entire northeast Pacific margin from southern California to the central Aleutian Islands, Alaska. Because exploitation/management histories and general habitat characteristics vary among these sites, we could examine the effects of prey diversity/availability and intra-specific competition on the prevalence of individual diet specialization. We used observational dietary data to quantify prey diversity and characterize relative habitat availability. We primarily relied on stable isotope data to quantify population and individual dietary variation and individuality. As in previous isotope-based studies of individuality, we defined the within-individual component (WIC) as the amount of intra-individual isotopic variation and the total isotopic niche width as the sum of the WIC and between-individual components (BIC). Results/Conclusions Using observational diet data, we classified half of our sites as rocky-substrate habitats, while the others contained a mixture of rocky substrate and soft-sediment habitats. Previous studies have shown that in rocky substrate habitats in California, individuality increases with intra-specific competition as measured by sea otter density. Our results, which include data for 8 rocky substrate sites from southern California to the central Aleutians, support previous findings. Specifically, the slope of the relationship between the within-individual component (WIC) and total isotopic niche width (TINW) was low (0.24) but significant (P<0.001, R2=0.90). Furthermore, population dietary diversity (TINW) was positively correlated with sea otter density. In contrast, the slope of the significant relationship (P<0.001, R2=0.95) between WIC and TINW for otter populations inhabiting mixed substrate sites was much higher (0.50), suggesting a low degree of individuality irrespective of competition (i.e., sea otter density). Our results show that the potential for individuality to occur as a result of increasing intra-specific competition is context dependent and that habitat characteristics, which ultimately influence prey diversity and abundance, are important in determining when and where individual specialization occurs in nature.
Archives of Environmental Contamination and Toxicology, 2009
Perfluorinated chemicals (PFCs) have been detected in abiotic and biotic matrices worldwide, incl... more Perfluorinated chemicals (PFCs) have been detected in abiotic and biotic matrices worldwide, including the Arctic Ocean. Considering these chemicals' persistent and bioaccumulative potentials, it was expected that levels of PFCs, like those of many legacy organic pollutants, would respond slowly to the restrictions in production and usage. Temporal trend studies in remote areas, such as the Arctic, can help determine the chronology of contamination and the response of the environment to regulations on PFCs. Prior to this study, temporal trends of PFCs in Alaskan coastal waters had not been examined. In the present study, concentrations of six PFCs were determined in livers of northern sea otters (Enhydra lutris kenyoni) collected from three areas in south-central Alaska (Prince William Sound, n = 36; Resurrection Bay, n = 7; Kachemak Bay, n = 34) from 1992 to 2007. Additionally, previously published profiles and concentrations of PFCs in southern sea otters from California and Asian sea otters from Kamchatka (Russia) were compared to our new data, to determine the geographical differences in PFC profiles among these three regions in the Pacific Ocean. Perfluorooctanesulfonate (PFOS), perfluorooctanesulfonamide (PFOSA), and perfluorononanoate (PFNA) were the predominant PFCs found in the livers of northern sea otters from 1992 to 2007. Other PFCs, such as perfluorooctanoate (PFOA), perfluoroundecanoate (PFUnDA), and perfluorodecanoate (PFDA), were detected less frequently, and at low concentrations. Overall, from 2001 to 2007, a decrease in concentrations of PFOS was found in northern sea otters, suggesting an immediate response to the phase-out in 2000 of perfluorooctanesulfonyl-based compounds by a major producer in the United States. In contrast, concentrations of PFNA in northern sea otters increased by 10-fold from 2004 to 2007. These results indicate that the contribution by PFNA to SigmaPFC concentrations is increasing in northern sea otters. The profiles (i.e., composition of individual PFC to SigmaPFC concentration) of PFCs in northern sea otters from Alaska were similar to those reported for southern sea otters from California, but were considerably different from the profiles reported for Asian sea otters from Russia, suggesting differences in point sources of exposure.
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