Under the climate change context, warming Southern Ocean waters may allow mercury (Hg) to become ... more Under the climate change context, warming Southern Ocean waters may allow mercury (Hg) to become more bioavailable to the Antarctic marine food web (i.e., ice-stored Hg release and higher methylation rates by microorganisms), whose biomagnification processes are poorly documented. Biomagnification of Hg in the food web of the Antarctic Peninsula, one of world's fastest warming regions, was examined using carbon (δ 13 C) and nitrogen (δ 15 N) stable isotope ratios for estimating feeding habitat and trophic levels, respectively. The stable isotope signatures and total Hg (T-Hg) concentrations were measured in Antarctic krill Euphausia superba and several Antarctic predator species, including seabirds (gentoo penguins Pygoscelis papua, chinstrap penguins Pygoscelis antarcticus, brown skuas Stercorarius antarcticus, kelp gulls Larus dominicanus, southern giant petrels Macronectes giganteus) and marine mammals (southern elephant seals Mirounga leonina). Significant differences in δ 13 C values among species were noted with a great overlap between seabird species and M. leonina. As expected, significant differences in δ 15 N values among species were found due to interspecific variations in diet related to their trophic position within the marine food web. The lowest Hg concentrations were registered in E. superba (0.007 ± 0.008 μg•g-1) and the highest values in M. giganteus (12.090 ± 14.177 μg•g-1). Additionally, a significant positive relationship was found between Hg concentrations and trophic levels (reflected by logarithm-transformed T-Hg values), biomagnifying nearly 2 times its concentrations each level. Our results support that trophic interactions are the major pathways for Hg biomagnification in Southern Ocean ecosystems and warn about an increase in the effects of Hg on long-lived (and high trophic level) Antarctic predators under climate change in the future.
In the Southern Ocean and adjacent waters, early stages of cephalopods play an important role in ... more In the Southern Ocean and adjacent waters, early stages of cephalopods play an important role in food webs as prey to top predators, but few is known regarding their biology and availability. Snares Penguin, Eudyptes robustus, is a top predator endemic to Snares Islands (New Zealand) that feed on cephalopods. As historical data on diet are rare for this species, Snares Penguins were used as biological samplers to evaluate the cephalopod component of its diet, where habitat and trophic level of cephalopods around the Snares Islands was assessed through stable isotope analysis. Moreover, ontogenic changes of juvenile squid were evaluated. Data collection were carried out during the breeding season 1986–87 and its analysis revealed that penguins fed on three juvenile cephalopod species: two squids (Nototodarus sloanii and Moroteuthopsis ingens) and one octopod (Octopus campbelli). Nototodarus sloanii was the most important species in frequency of occurrence and mass, whereas M. ingens was the most important in number. Juvenile squid species showed similar δ13C values, suggesting both occupied similar habitats on the Snares shelf, whereas juvenile O. campbelli showed lower δ13C values. Moreover, O. campbelli fed on higher trophic level (δ15N) prey relative to squid species. Lower diversity and larger sizes of cephalopods were found when compared with data from 2002. This study shows that Snares Penguin can be a good local biological sampler of juvenile cephalopods during their breeding season, providing both essential biogeographic information of cephalopod diversity and relevant historical information for the conservation of this endemic penguin species.
Sardines (Sardina pilchardus) and mackerels (Scomber spp. and Trachurus spp.) are amongst the mos... more Sardines (Sardina pilchardus) and mackerels (Scomber spp. and Trachurus spp.) are amongst the most common fish caught along the Iberian coast for human consumption and, as mid-trophic level organisms, they constitute essential prey in the diet of several marine predators. Thus, the assessment of trophic ecology, contamination exposure, and stress responses in such organisms provides valuable information on the environmental health in the mid-trophic chain and the potential risks for consumers. This study aims to contribute for an integrative mercury assessment of the marine ecosystem by measuring stable isotopes, mercury levels, and oxidative stress parameters in five commercial fish species in the northeast Atlantic. Samples of muscle and liver were collected from a total of 116 individuals in two fisheries assessment surveys (Spring and Autumn) along the whole Portuguese coast. Mercury concentrations and stable isotope analysis (δ 13 C and δ 15 N) were performed in the muscle, while oxidative stress parameters (lipid peroxidation and DNA damage) were measured in both muscle and liver. Mercury concentrations were found to be considerably lower than values recorded in previous studies and the limits set by the European Union law, which confirms the non-toxic status of these species along the Portuguese coast, concerning this harmful element. Interestingly, no differences were found among the three genera, despite clear differences in trophic niches. Still, mercury concentrations were significantly higher during Autumn than Spring, possibly due to upwelling events during the Summer. Moreover, no relationships between the mercury concentrations and oxidative stress parameters were found. Overall, this work provided an integrative mercury assessment of commercial fishes from the mid-trophic chain, particularly from pelagic (and neritic) regions in the northeast Atlantic, showing that mercury concentration in these species is low. However, it is important to note that this study focused on small-and medium-sized specimens (overall ranging from 13-25 cm in length), and thus higher concentrations of mercury may be present in larger fish due to bioaccumulation.
Gulls are highly opportunistic seabirds, and the exploitation of fishery discards has led to many... more Gulls are highly opportunistic seabirds, and the exploitation of fishery discards has led to many population increases worldwide. We investigated the importance of fish in the diet of yellow-legged Larus michahellis and Audouin’s gulls L. audouinii and assessed the influence of fishery discards on their feeding ecology. We collected pellets from 4 islands along the western Iberian coast during pre-breeding, breeding, and post-breeding seasons from 2014 to 2018. Stable isotopes (from adult blood, and chick and adult feathers) were used to investigate spatial, seasonal, and inter-annual differences in their feeding ecology. We used pellet, stable isotope (δ15N, δ13C, and δ34S), and biochemical (triglycerides, uric acid, total protein, and carotenoids in adult plasma) analyses to investigate their relationships with fish landings across the annual cycle. Results revealed that the fish species consumed by gulls matched those landed by local fisheries on all study islands, and there was ...
In recent decades, the breeding populations of the yellow-legged gull Larus michahellis (YLG) hav... more In recent decades, the breeding populations of the yellow-legged gull Larus michahellis (YLG) have increased significantly, primarily due to the increase in open refuse dumps and discards from fisheries. Portugal’s largest YLG breeding colony is located on Berlenga Island, where population numbers have been monitored since 1974. The population grew exponentially until 1994, prompting the implementation of population control measures, including culling adult birds and eggs. A long-term data base including number of breeding birds (since 1974), breeding parameters (since 2002), and trophic niches (using stable isotopes since 2011) of YLG breeding on Berlenga was related with oceanographic parameters, fish landings and quantity of urban waste. Trophic ecology showed strong relationships with oceanographic parameters (wNAO, Chl-a, and SST) and fisheries landings (the 10 most frequently consumed species by the YLG, traded at fish auctions in the main fishing harbour nearby). The results ...
Marques JC, Ramos JA. Annual and seasonal consistency in the feeding ecology of an opportunistic ... more Marques JC, Ramos JA. Annual and seasonal consistency in the feeding ecology of an opportunistic species, the yellow-legged gull (Larus michahellis). Marine Ecology Progress Series (accepted for publication).
Cephalopods are important in Arctic marine ecosystems as predators and prey, but knowledge of the... more Cephalopods are important in Arctic marine ecosystems as predators and prey, but knowledge of their life cycles is poor. Consequently, they are under-represented in the Arctic ecosystems assessment models. One important parameter is the change in ecological role (habitat and diet) associated with individual ontogenies. Here, the life history of Gonatus fabricii, the most abundant Arctic cephalopod, is reconstructed by the analysis of individual ontogenetic trajectories of stable isotopes (δ13C and δ15N) in archival hard body structures. This approach allows the prediction of the exact mantle length (ML) and mass when the species changes its ecological role. Our results show that the life history of G. fabricii is divided into four stages, each having a distinct ecology: (1) epipelagic squid (ML < 20 mm), preying mostly on copepods; (2) epi- and occasionally mesopelagic squid (ML 20–50 mm), preying on larger crustaceans, fish, and cephalopods; (3) meso- and bathypelagic squid (ML ...
Cephalopods play a major role in marine ecosystems, yet very little is known about the dynamics o... more Cephalopods play a major role in marine ecosystems, yet very little is known about the dynamics of their habitat use and trophic ecology across the stages of their life cycle, particularly in the Southern Ocean. Here, we used stable isotope analyses of δ13C (a proxy for foraging habitat) and δ15N (a proxy for trophic position) to investigate the habitat use and trophic ecology of 10 squid species, collected from the diet of Antipodean (Diomedea antipodensis antipodensis) and Gibson’s (D. a. gibsoni) albatrosses breeding at Antipodes and Adams Island (South Pacific), respectively. We analyzed isotopes in 2 sections of squid lower beaks, representing 2 stages of the life cycle: the tip of the rostrum (juvenile stage) and the wing (adult stage). Higher δ13C values in early life stages (-20.8 ± 1.7‰) than in adult life stages (-21.6 ± 1.9‰) suggest that Southern Ocean squids tend to move southwards as they grow, with oceanic fronts being an important habitat for these species. Our resul...
According to the principles of community ecology, sympatric species may suffer a selective pressu... more According to the principles of community ecology, sympatric species may suffer a selective pressure to decrease their niche overlap through mechanisms of niche partitioning. However, there is still a gap in knowledge of the main drivers influencing niche differentiation, particularly in communities composed by small-sized and inconspicuous species. The coastal epipelagic community structure of mid-trophic level species in the Northeast Atlantic was examined using stable isotope analysis to (1) decipher intrinsic and extrinsic factors promoting niche partitioning and (2) examine species divergence in the use of resources. A total of 474 individuals from a guild of 11 species were sampled during three years, and the influence of potential drivers of isotopic divergence was assessed. The niche partitioning was mainly determined by the taxonomic group in accordance with the fundamental principles of niche theory, which was consistent for both δ13C (i.e. habitat) and δ15N (i.e. prey). Bo...
Studies on sex-specific segregation in foraging and trophic niche have been focused on large and ... more Studies on sex-specific segregation in foraging and trophic niche have been focused on large and dimorphic seabirds, with less information on small monomorphic species. Here, we used mini-GPS loggers, habitat suitability models, and stable isotopes to assess the foraging movements, at-sea spatial distribution, and trophic ecology of male and female Boyd’s shearwaters Puffinus lherminieri boydi in Raso Islet (16°36’ N, 24°35’ W), Cabo Verde, during the breeding seasons of 2018–2019. The existence of sexual foraging segregation was tested in short and long foraging trips. Females engaged on longer foraging trips, travelling towards more distant and northward regions from the colony when compared to males, especially during long foraging excursions. Spatial overlap within and between sexes was generally low, indicating a sex-specific pattern in the foraging behaviour and spatial distribution of adult breeders. Habitat suitability models revealed a higher importance for chlorophyll a co...
Raw data from the research article 'Assessment of environmental health based on a complementa... more Raw data from the research article 'Assessment of environmental health based on a complementary approach using metal quantification, oxidative stress and trophic ecology of two gull species (Larus michahellis & Larus audouinii) breeding in sympatry
Under the climate change context, warming Southern Ocean waters may allow mercury (Hg) to become ... more Under the climate change context, warming Southern Ocean waters may allow mercury (Hg) to become more bioavailable to the Antarctic marine food web (i.e., ice-stored Hg release and higher methylation rates by microorganisms), whose biomagnification processes are poorly documented. Biomagnification of Hg in the food web of the Antarctic Peninsula, one of world's fastest warming regions, was examined using carbon (δ 13 C) and nitrogen (δ 15 N) stable isotope ratios for estimating feeding habitat and trophic levels, respectively. The stable isotope signatures and total Hg (T-Hg) concentrations were measured in Antarctic krill Euphausia superba and several Antarctic predator species, including seabirds (gentoo penguins Pygoscelis papua, chinstrap penguins Pygoscelis antarcticus, brown skuas Stercorarius antarcticus, kelp gulls Larus dominicanus, southern giant petrels Macronectes giganteus) and marine mammals (southern elephant seals Mirounga leonina). Significant differences in δ 13 C values among species were noted with a great overlap between seabird species and M. leonina. As expected, significant differences in δ 15 N values among species were found due to interspecific variations in diet related to their trophic position within the marine food web. The lowest Hg concentrations were registered in E. superba (0.007 ± 0.008 μg•g-1) and the highest values in M. giganteus (12.090 ± 14.177 μg•g-1). Additionally, a significant positive relationship was found between Hg concentrations and trophic levels (reflected by logarithm-transformed T-Hg values), biomagnifying nearly 2 times its concentrations each level. Our results support that trophic interactions are the major pathways for Hg biomagnification in Southern Ocean ecosystems and warn about an increase in the effects of Hg on long-lived (and high trophic level) Antarctic predators under climate change in the future.
In the Southern Ocean and adjacent waters, early stages of cephalopods play an important role in ... more In the Southern Ocean and adjacent waters, early stages of cephalopods play an important role in food webs as prey to top predators, but few is known regarding their biology and availability. Snares Penguin, Eudyptes robustus, is a top predator endemic to Snares Islands (New Zealand) that feed on cephalopods. As historical data on diet are rare for this species, Snares Penguins were used as biological samplers to evaluate the cephalopod component of its diet, where habitat and trophic level of cephalopods around the Snares Islands was assessed through stable isotope analysis. Moreover, ontogenic changes of juvenile squid were evaluated. Data collection were carried out during the breeding season 1986–87 and its analysis revealed that penguins fed on three juvenile cephalopod species: two squids (Nototodarus sloanii and Moroteuthopsis ingens) and one octopod (Octopus campbelli). Nototodarus sloanii was the most important species in frequency of occurrence and mass, whereas M. ingens was the most important in number. Juvenile squid species showed similar δ13C values, suggesting both occupied similar habitats on the Snares shelf, whereas juvenile O. campbelli showed lower δ13C values. Moreover, O. campbelli fed on higher trophic level (δ15N) prey relative to squid species. Lower diversity and larger sizes of cephalopods were found when compared with data from 2002. This study shows that Snares Penguin can be a good local biological sampler of juvenile cephalopods during their breeding season, providing both essential biogeographic information of cephalopod diversity and relevant historical information for the conservation of this endemic penguin species.
Sardines (Sardina pilchardus) and mackerels (Scomber spp. and Trachurus spp.) are amongst the mos... more Sardines (Sardina pilchardus) and mackerels (Scomber spp. and Trachurus spp.) are amongst the most common fish caught along the Iberian coast for human consumption and, as mid-trophic level organisms, they constitute essential prey in the diet of several marine predators. Thus, the assessment of trophic ecology, contamination exposure, and stress responses in such organisms provides valuable information on the environmental health in the mid-trophic chain and the potential risks for consumers. This study aims to contribute for an integrative mercury assessment of the marine ecosystem by measuring stable isotopes, mercury levels, and oxidative stress parameters in five commercial fish species in the northeast Atlantic. Samples of muscle and liver were collected from a total of 116 individuals in two fisheries assessment surveys (Spring and Autumn) along the whole Portuguese coast. Mercury concentrations and stable isotope analysis (δ 13 C and δ 15 N) were performed in the muscle, while oxidative stress parameters (lipid peroxidation and DNA damage) were measured in both muscle and liver. Mercury concentrations were found to be considerably lower than values recorded in previous studies and the limits set by the European Union law, which confirms the non-toxic status of these species along the Portuguese coast, concerning this harmful element. Interestingly, no differences were found among the three genera, despite clear differences in trophic niches. Still, mercury concentrations were significantly higher during Autumn than Spring, possibly due to upwelling events during the Summer. Moreover, no relationships between the mercury concentrations and oxidative stress parameters were found. Overall, this work provided an integrative mercury assessment of commercial fishes from the mid-trophic chain, particularly from pelagic (and neritic) regions in the northeast Atlantic, showing that mercury concentration in these species is low. However, it is important to note that this study focused on small-and medium-sized specimens (overall ranging from 13-25 cm in length), and thus higher concentrations of mercury may be present in larger fish due to bioaccumulation.
Gulls are highly opportunistic seabirds, and the exploitation of fishery discards has led to many... more Gulls are highly opportunistic seabirds, and the exploitation of fishery discards has led to many population increases worldwide. We investigated the importance of fish in the diet of yellow-legged Larus michahellis and Audouin’s gulls L. audouinii and assessed the influence of fishery discards on their feeding ecology. We collected pellets from 4 islands along the western Iberian coast during pre-breeding, breeding, and post-breeding seasons from 2014 to 2018. Stable isotopes (from adult blood, and chick and adult feathers) were used to investigate spatial, seasonal, and inter-annual differences in their feeding ecology. We used pellet, stable isotope (δ15N, δ13C, and δ34S), and biochemical (triglycerides, uric acid, total protein, and carotenoids in adult plasma) analyses to investigate their relationships with fish landings across the annual cycle. Results revealed that the fish species consumed by gulls matched those landed by local fisheries on all study islands, and there was ...
In recent decades, the breeding populations of the yellow-legged gull Larus michahellis (YLG) hav... more In recent decades, the breeding populations of the yellow-legged gull Larus michahellis (YLG) have increased significantly, primarily due to the increase in open refuse dumps and discards from fisheries. Portugal’s largest YLG breeding colony is located on Berlenga Island, where population numbers have been monitored since 1974. The population grew exponentially until 1994, prompting the implementation of population control measures, including culling adult birds and eggs. A long-term data base including number of breeding birds (since 1974), breeding parameters (since 2002), and trophic niches (using stable isotopes since 2011) of YLG breeding on Berlenga was related with oceanographic parameters, fish landings and quantity of urban waste. Trophic ecology showed strong relationships with oceanographic parameters (wNAO, Chl-a, and SST) and fisheries landings (the 10 most frequently consumed species by the YLG, traded at fish auctions in the main fishing harbour nearby). The results ...
Marques JC, Ramos JA. Annual and seasonal consistency in the feeding ecology of an opportunistic ... more Marques JC, Ramos JA. Annual and seasonal consistency in the feeding ecology of an opportunistic species, the yellow-legged gull (Larus michahellis). Marine Ecology Progress Series (accepted for publication).
Cephalopods are important in Arctic marine ecosystems as predators and prey, but knowledge of the... more Cephalopods are important in Arctic marine ecosystems as predators and prey, but knowledge of their life cycles is poor. Consequently, they are under-represented in the Arctic ecosystems assessment models. One important parameter is the change in ecological role (habitat and diet) associated with individual ontogenies. Here, the life history of Gonatus fabricii, the most abundant Arctic cephalopod, is reconstructed by the analysis of individual ontogenetic trajectories of stable isotopes (δ13C and δ15N) in archival hard body structures. This approach allows the prediction of the exact mantle length (ML) and mass when the species changes its ecological role. Our results show that the life history of G. fabricii is divided into four stages, each having a distinct ecology: (1) epipelagic squid (ML < 20 mm), preying mostly on copepods; (2) epi- and occasionally mesopelagic squid (ML 20–50 mm), preying on larger crustaceans, fish, and cephalopods; (3) meso- and bathypelagic squid (ML ...
Cephalopods play a major role in marine ecosystems, yet very little is known about the dynamics o... more Cephalopods play a major role in marine ecosystems, yet very little is known about the dynamics of their habitat use and trophic ecology across the stages of their life cycle, particularly in the Southern Ocean. Here, we used stable isotope analyses of δ13C (a proxy for foraging habitat) and δ15N (a proxy for trophic position) to investigate the habitat use and trophic ecology of 10 squid species, collected from the diet of Antipodean (Diomedea antipodensis antipodensis) and Gibson’s (D. a. gibsoni) albatrosses breeding at Antipodes and Adams Island (South Pacific), respectively. We analyzed isotopes in 2 sections of squid lower beaks, representing 2 stages of the life cycle: the tip of the rostrum (juvenile stage) and the wing (adult stage). Higher δ13C values in early life stages (-20.8 ± 1.7‰) than in adult life stages (-21.6 ± 1.9‰) suggest that Southern Ocean squids tend to move southwards as they grow, with oceanic fronts being an important habitat for these species. Our resul...
According to the principles of community ecology, sympatric species may suffer a selective pressu... more According to the principles of community ecology, sympatric species may suffer a selective pressure to decrease their niche overlap through mechanisms of niche partitioning. However, there is still a gap in knowledge of the main drivers influencing niche differentiation, particularly in communities composed by small-sized and inconspicuous species. The coastal epipelagic community structure of mid-trophic level species in the Northeast Atlantic was examined using stable isotope analysis to (1) decipher intrinsic and extrinsic factors promoting niche partitioning and (2) examine species divergence in the use of resources. A total of 474 individuals from a guild of 11 species were sampled during three years, and the influence of potential drivers of isotopic divergence was assessed. The niche partitioning was mainly determined by the taxonomic group in accordance with the fundamental principles of niche theory, which was consistent for both δ13C (i.e. habitat) and δ15N (i.e. prey). Bo...
Studies on sex-specific segregation in foraging and trophic niche have been focused on large and ... more Studies on sex-specific segregation in foraging and trophic niche have been focused on large and dimorphic seabirds, with less information on small monomorphic species. Here, we used mini-GPS loggers, habitat suitability models, and stable isotopes to assess the foraging movements, at-sea spatial distribution, and trophic ecology of male and female Boyd’s shearwaters Puffinus lherminieri boydi in Raso Islet (16°36’ N, 24°35’ W), Cabo Verde, during the breeding seasons of 2018–2019. The existence of sexual foraging segregation was tested in short and long foraging trips. Females engaged on longer foraging trips, travelling towards more distant and northward regions from the colony when compared to males, especially during long foraging excursions. Spatial overlap within and between sexes was generally low, indicating a sex-specific pattern in the foraging behaviour and spatial distribution of adult breeders. Habitat suitability models revealed a higher importance for chlorophyll a co...
Raw data from the research article 'Assessment of environmental health based on a complementa... more Raw data from the research article 'Assessment of environmental health based on a complementary approach using metal quantification, oxidative stress and trophic ecology of two gull species (Larus michahellis & Larus audouinii) breeding in sympatry
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