Search

In the Southern Chukchi Sea Region (SCSR) of the Alaskan Arctic, approximately 40% of the coastline consists of freshwater-brackish lagoons and the gravel spits that separate them from the ocean. These lagoons are important rearing, feeding, and spawning habitats for diverse fish and invertebrate assemblages composed of freshwater, diadromous, and marine taxa. Many of these species are prey for a suite of marine mammals and avian predators in addition to being important to the food security of subsistence users from the surrounding region. Despite recognition of the ecological and cultural importance of these habitats from as far back as the 1950s, the body of knowledge surrounding lagoons of the SCSR contains many knowledge gaps and fails to comprehensively capture the dynamic nature of both biotic and abiotic factors that define the functional ecology of these habitats. This report synthesizes the available knowledge of SCSR lagoons, including geomorphology, hydrology, food web structure, and local knowledge. We also recommend avenues of future study, such as characterizing the basal trophic levels of lagoon food webs. Only by constructing a more detailed and comprehensive knowledge base of SCSR lagoon ecology will management and conservation efforts in the region be able to address and mitigate potential threats resulting from expanding infrastructure and global climate change, while simultaneously supporting the diverse portfolio of lagoon habitats that have a vital role in regional subsistence practices and food security.

Arctic coastal lagoons are important habitats for unique assemblages of diadromous and marine fishes. Many of these fishes are vital to the food security of rural and indigenous communities. However, human impacts on coastal Arctic habitats, as well as climate change, weaken ecosystem resiliency and threaten the sustainability of fish stocks as a component of local food security. Identifying how habitat characteristics influence fish ecology may allow for predictions of changes in fish abundance and availability in response to these threats, and may help illuminate strategies for responding to negative impacts. Consequently, we endeavored to link habitat characteristics likely to be most-impacted by climate change to fish assemblage trophic metrics in four lagoons within Cape Krusenstern National Monument, Alaska where subsistence fishing commonly occurs. This was done through calculating trophic metrics including mean nitrogen (δ15N) and carbon (δ13C) stable isotope values from fish muscle tissue samples collected from the study lagoons. Lagoon habitat characteristics were quantified including ocean connectivity, freshwater input, and surface area using satellite imagery. Finally, associations between fish assemblage trophic metrics and habitat characteristics were evaluated using linear regressions, and trophic metrics were compared between lagoons with ANOVA and Tukey post-hoc tests. Model results showed that increased freshwater input resulted in longer duration of lagoon ocean connectivity. Additionally, longer duration of ocean connectivity was associated with an increase in mean δ15N and δ13C across all lagoon fish species. Finally, there were significant species-specific differences in fish trophic metrics among lagoons with varying habitat characteristics. Overall, freshwater input and ocean connectivity of coastal Arctic lagoons appear to be important drivers of fish trophic ecology, and should be carefully monitored in the face of anticipated changes in the region, to conserve important subsistence harvest species.

1. Hardbottom habitats of Biscayne Bay, a shallow lagoon adjacent to the city of Miami, Florida, USA, contain a limited number of coral species that represent a small subset of the species found at nearby offshore hardbottom and reef habitats of the Florida Reef Tract. Although the physical characteristics of this basin make it a marginal environment for coral growth, the presence of dense populations of Siderastrea radians and Porites furcata indicate that these, as well as other corals that are found at lower densities, are able to tolerate extreme and fluctuating conditions. Three factors, temperature, sedimentation, and salinity, appear to limit coral abundance, diversity, and distribution within Biscayne Bay. 2. Temperatures exhibit high frequencies of extreme high and low values known to cause coral stress and mortality elsewhere. Similarly, sedimentation rates are very high and sediment resuspension caused by currents, storms and boating activities commonly bury corals under sediment layers. Sediment burial was shown experimentally to influence growth and mortality of S. radians. 3. The salinity of Biscayne Bay is influenced by freshwater inputs from canal, sheetflow and groundwater sources that create a near-shore environment with low mean salinity and high salinity fluctuation. Coral communities along this western margin have the lowest coral density and species richness. Chronic exposure to low salinity was shown experimentally to cause a decrease in the growth of S. radians. 4. The location of Biscayne Bay, downstream of a large restoration effort planned for the Everglades watershed, highlights the need to understand the relationship between the physical environment and the health of benthic communities. The data presented here provide the type of scientific information needed so that management decisions can take into account the potential impacts of human activities on the health of coral populations that are already near their tolerance limits for temperature, salinity, and sedimentation. Copyright © 2003 John Wiley & Sons, Ltd.