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1. Arctic lagoon and nearshore food webs: Relative contributions of terrestrial organic matter, phytoplankton, and phytobenthos vary with consumer foraging dynamics

   https://doi.org/https://doi.org/10.1016/j.ecss.2021.107388  

   McMahon, Kelton W; Ambrose, William G.; Reynolds, Melinda J.; Johnson, Beverly; Whiting, A.; Clough, Lisa M. (May 2021, Estuarine coastal and shelf science)

   null (Ed.)

   Characterizing energy flow and trophic linkages is fundamental to understanding the functioning and resilience of Arctic ecosystems under increasing pressure from climate change and anthropogenic exploitation. We used carbon and nitrogen stable isotopes to examine trophic dynamics and the relative contribution of terrestrial organic matter, water column phytoplankton, and phytobenthos (benthic micro- and macro-autotrophs as well as sea ice algae) to the food webs supporting 45 macroconsumers in three Arctic coastal lagoon ecosystems (Krusenstern, Sisualik, Akulaaq) and the adjacent Kotzebue Sound with varying degrees of connectivity in Cape Krusenstern National Monument, Alaska. A two-source (water column particulate organic matter and benthic sediment organic matter), two-isotope trophic dynamics model informed by a Bayesian isotope mixing model revealed that the Lagoon-Kotzebue Sound coastal ecosystem supported consumers along a trophic position continuum from primary consumers, including amphipods, copepods, and clams to trophic level five predators, such as seastars, piscivorous fishes, seals, and seabirds. The relative contribution of the three primary producer end members, terrestrial organic matter (41 ± 21%), phytoplankton (25 ± 21%), and phytobenthos (34 ± 23%) varied as a function of: 1) consumer foraging ecology and 2) consumer location. Suspension feeders received most of their carbon from food webs based on phytoplankton (49 ± 11%) and terrestrial organic matter (23 ± 5%), whereas herbivores and detritivores received the majority of their carbon from phytobenthos-based food webs, 58 ± 10% and 60 ± 8%, respectively. Omnivores and predators showed more even distributions of resource reliance and greater overall variance among species. Within the invertebrates, the importance of terrestrial organic matter decreased and phytobenthos increased with increasing trophic position. The importance of terrestrial organic matter contribution increased with lagoon proximity to major rivers inputs and isolation from Kotzebue Sound. Several taxa with cultural and subsistence food importance to local communities showed significant reliance (30–90% of baseline carbon) on food chains linked to fresh terrestrial organic matter. Our study indicates that terrestrial-marine linkages are important to the function of Arctic coastal lagoon ecosystems and artisanal fisheries. These linkages are likely to strengthen in the future with regional changes in erosion and runoff associated with climate change and anthropogenic disturbance. 

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2. DNA metabarcoding of feces to infer summer diet of Pacific walruses

   https://doi.org/10.1111/mms.12717  

   Sonsthagen, Sarah_A; Jay, Chadwick_V; Cornman, Robert_S; Fischbach, Anthony_S; Grebmeier, Jacqueline_M; Talbot, Sandra_L (July 2020, Marine Mammal Science)

   Abstract Environmental conditions in the Chukchi Sea are changing rapidly and may alter the abundance and distribution of marine species and their benthic prey. We used a metabarcoding approach to identify potentially important prey taxa from Pacific walrus (Odobenus rosmarus divergens) fecal samples (n= 87). Bivalvia was the most dominant class of prey (66% of all normalized counts) and occurred in 98% of the samples. Polychaeta and Gastropoda occurred in 70% and 62% of the samples, respectively. The remaining nine invertebrate classes comprised <21% of all normalized counts. The common occurrence of these three prey classes is consistent with examinations of walrus stomach contents. Despite these consistencies, biases in the metabarcoding approach to determine diet from feces have been highlighted in other studies and require further study, in addition to biases that may have arisen from our opportunistic sampling. However, this noninvasive approach provides accurate identification of prey taxa from degraded samples and could yield much‐needed information on shifts in walrus diet in a rapidly changing Arctic. 

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3. Co-producing knowledge about the Pacific walrus and climate change

   https://doi.org/10.1139/as-2024-0061  

   Metcalf, Vera; Apassingok, Daniel; Campbell, Iver; Gologergen, Arnold; Gologergen, Bivers; Noongwook, Edwin; Huntington, Henry P; Garlich-Miller, Joel L; Johnson, Devin L (January 2025, Arctic Science)

   Pacific walruses ( Odobenus rosmarus divergens, Illiger 1815) have long been vital to Indigenous communities along Alaska’s west coast. Although current harvest rates are sustainable, climate change and increased industrial activity in the range of this species pose threats to the population and to hunting safety and success. To gather information relevant to addressing these concerns, the Eskimo Walrus Commission and the US Fish and Wildlife Service held a workshop in August 2023 in Nome, Alaska, with experienced Yupik walrus hunters from the communities of Gambell and Savoonga on St. Lawrence Island, Alaska, and Federal walrus biologists. The 3-day event documented extensive information about walrus biology and behavior, which was used to improve a walrus population model. Workshop discussions also addressed concepts of sustainability and the future of walrus hunting. The workshop benefitted from prior collaboration between the biologists and some of the hunters on a walrus research cruise in the Chukchi Sea earlier the same summer, creating a foundation of common experience and interpersonal relationships. In the longer term, the workshop helped demonstrate the value of equitable collaboration towards shared goals, in part by allowing for open conversations rather than, for example, an extended question-and-answer session regarding model parameters. 

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4. Prevalence of pelagic diatoms and harmful algae in tellinid bivalve diets during record low sea ice in the Pacific Arctic determined by DNA metabarcoding

   https://doi.org/10.3389/fmars.2025.1480327  

   Koch, Chelsea W; Sonsthagen, Sarah A; Cooper, Lee W; Grebmeier, Jacqueline M; Riddle-Berntsen, Ann E; Cornman, Robert S (February 2025, Frontiers in Marine Science)

   Understanding changes at the base of the marine food web in the rapidly transforming Arctic is essential for predicting and evaluating ecosystem dynamics. The northern Bering Sea experienced record low sea ice in 2018, followed by the second lowest in 2019, highlighting the urgency of the issue for this region. In this study, we investigated the diet of the clamMacoma calcareain the Pacific Arctic using DNA metabarcoding, employing 18S and rbcL markers to identify dietary components. Our findings revealed a strong dependence on pelagic diatoms, particularlyChaetocerossp., with a near absence of ice algae in the clam diet. This pattern reflects the lack of lipid-rich ice algal production during these low sea ice events. Additionally, our analysis detected algae capable of producing harmful toxins, notablyAlexandriumdinoflagellates, in the clam diet, underscoring the need for increased monitoring due to potential ecosystem and human health risks. This study demonstrates the utility of DNA metabarcoding in unraveling the complex dynamics of Arctic marine food webs and pelagic-benthic coupling, providing a glimpse of future conditions in a rapidly changing environment. 

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5. Macroalgal input into the coastal food web along a gradient of seasonal sea ice cover along the Western Antarctic Peninsula

   https://doi.org/10.3354/meps14388  

   Iken, K; Amsler, CD; Gorman, KB; Klein, AG; Galloway, AWE; Amsler, MO; Heiser, S; Whippo, R; Lowe, AT; Schram, JB; et al (September 2023, Marine Ecology Progress Series)

   Coastal food webs that are supported by multiple primary producer sources are considered to be more stable against perturbations. Here, we investigated how declining macroalgal abundance and diversity might influence coastal food web structure along an annual sea ice cover gradient along the Western Antarctic Peninsula (WAP). The most common benthic invertebrate consumers, macroalgae, and surface particulate organic matter were collected at 15 stations along the WAP. Stable carbon and nitrogen isotope values of primary producers changed negligibly in relation to the sea ice cover gradient, while isotope values of most invertebrate feeding groups increased with higher sea ice cover, although at low explanatory power. Food web length became shorter and consumer trophic niche width smaller in regions with higher sea ice cover. Changes in food web structure were mostly associated with shifts in trophic position of lower trophic levels. Food web structure in higher ice-covered regions resembled that of more generalist feeders with a loss of specialist species, concurrent with an increased reliance on a more reworked detrital food source. These results suggest that a number of benthic invertebrates are able to adjust to differences in basal energy sources. Conversely, these food webs dominated by generalist feeders are likely less efficient in energy transfer, which can create less-stable systems with lower adaptive capacity to disturbance. The predicted sea ice loss along the WAP may ultimately lead to a longer food web with higher macroalgal abundance, more specialist species, and wider consumer trophic niches in the currently more ice-covered regions. 

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