Larval Dispersal Modeling Suggests Limited Ecological Connectivity Between Fjords on the West Antarctic Peninsula

Abstract

<jats:title>Abstract</jats:title> <jats:p>Larval dispersal is a key process for community assembly and population maintenance in the marine environment, yet it is extremely difficult to measure at ecologically relevant spatio-temporal scales. We used a high-resolution hydrodynamic model and particle-tracking model to explore the dispersal of simulated larvae in a hydrographically complex region of fjords on the West Antarctic Peninsula. Modeled larvae represented two end members of dispersal potential observed in Antarctic benthos resulting from differing developmental periods and swimming behavior. For simulations of low dispersing larvae (pre-competency period= 8 days, settlement period= 15 days, swimming downward) self-recruitment within fjords was important, with no larval settlement occurring in adjacent fjords &amp;lt; 50 km apart. For simulations of highly dispersing organisms (pre-competency period= 35-120 days, settlement period= 30-115 days, no swimming behavior), dispersal between fjords occurred when larvae were in the water column for at least 35 days, but settlement was rarely successful even for larvae spending up to 150 days in the plankton. The lack of ecological connectivity between fjords within a single spawning event suggests that these fjords harbor ecologically distinct populations in which self-recruitment may maintain populations, and genetic connectivity between fjords is likely achieved through stepping-stone dispersal. Export of larvae from natal fjord populations to the broader shelf region (&amp;gt; 100 km distance) occurred within surface layers (&amp;lt; 100 m depth) and was enhanced by episodic katabatic wind events that may be common in glaciomarine fjords worldwide.</jats:p>

Phytoplankton dynamics in nearshore regions of the western Antarctic Peninsula in relation to a variable frontal zone in the Gerlache Strait

“…Modeling by Hahn-Woernle et al ( 2020) found a significant exchange of surface waters between Andvord Bay and the Gerlache Strait, which causes the fjord to lose or gain heat, mainly driven by winds. In addition, both planktonic organisms (larvae), chlorophyll a, and macro-and micronutrients originating within the fjords can be exported to the Gerlache Strait within a month, an exchange strongly enhanced by recurrent katabatic winds (Ekern, 2017;Ziegler et al, 2020;Forsch et al, 2021). Similar processes have been reported for Arthur Harbor in Anvers Island and Southeast Greenland, suggesting wind-driven exchange of surface waters is a common process in high-latitude nearshore areas (Moline and Prezelin, 1996;Spall et al, 2017).…”

“…The waters of the Gerlache Strait are characterized by long residence times that can range from weeks to months and it is estimated that within coastal areas this residence time may be longer (Zhou et al, 2002), which may explain this interconnectedness between coastal areas and the long persistence of phytoplankton assemblages. Studies from Andvord Bay can explain the interconnectedness between the Strait and the coastal areas affecting inshore phytoplankton assemblages (Ekern, 2017;Lundesgaard et al, 2019;Hahn-Woernle et al, 2020;Lundesgaard et al, 2020;Ziegler et al, 2020;Forsch et al, 2021). Modeling by Hahn-Woernle et al ( 2020) found a significant exchange of surface waters between Andvord Bay and the Gerlache Strait, which causes the fjord to lose or gain heat, mainly driven by winds.…”

Antarctic ecosystem responses following ice‐shelf collapse and iceberg calving: Science review and future research

“…A major challenge is to document ecosystem responses at all levels of biological organization (genome to pan‐Antarctic), and combine genomics/DNA approaches with multi‐taxon studies that integrate taxonomic, biogeochemical, genomic, and community data followed by matching biological data with fluxes/transports measured by physical oceanographers, geochemists, and geologists (e.g., Halanych & Mahon, 2018). We also need a better understanding of the mechanistic linkages between climate, sea ice and ice shelves, ice sheets and icebergs, biogeochemical processes, food webs and organism interactions, and population and community dynamics (e.g., Lundesgaard et al, 2020; Ziegler, Cape, et al, 2020; Ziegler, Hahn‐Woernle, et al, 2020). Linkages with glaciology, physical oceanography, biology, and ecological interactions are critical as both drivers and impacts of ice‐shelf loss (Ducklow, 2008; Ducklow et al, 2007; Massom & Stammerjohn, 2010).…”