Functional implications of changes in seagrass species composition in two shallow coastal lagoons

Abstract

While the consequences of losing seagrass meadows are well known, there is less information on the functional implications of changes in seagrass species composition. In this study, we use data from a long-term monitoring project in shallow lagoons on the Florida Gulf Coast to assess changes in the functional attributes of seagrass beds during a shift in seagrass species composition. We compare seagrass beds in 2 neighboring lagoons with different trends: one where the composition changed from 100% Halodule wrightii to a mixed bed with up to 60% Ruppia maritima, and one where the species composition remained unchanged. Our results indicate that the partial replacement of H. wrightii by R. maritima did not alter seagrass biomass m , benthic gross primary production, or benthic respiration. However, there was a small positive effect on benthic net primary production. While seagrass biomass m −2 declined at both sites, the emergence of R. maritima increased the amount of available habitat through rapid expansion. Overall, our data suggest that shifts between 2 seagrass species with similar morphology, but different ecological strategies, may have little impact on the ecosystem services of seagrass beds in shallow coastal lagoons.

Effects of small‐scale, shading‐induced seagrass loss on blue carbon storage: Implications for management of degraded seagrass ecosystems

“…Annual water temperatures in the study site typically ranged from c . 10 to 30°C (Christiaen, Lehrter, Goff, & Cebrian, ). Big Lagoon is a narrow sound surrounded by large mass lands on both sides carpeted with many tidal creeks and inlets.…”

“…There is clear zonation between the two species, with monospecific Halodule stands closest to the shoreline, followed by mixed stands further from the shoreline, then Thalassia-only stands. Annual water temperatures in the study site typically ranged from c. 10 to 30°C (Christiaen, Lehrter, Goff, & Cebrian, 2016). Big Lagoon is a narrow sound surrounded by large mass lands on both sides carpeted with many tidal creeks and inlets.…”

Understanding the Long-Term Evolution of the Coupled Natural-Human Coastal System: The Future of the U.S. Gulf Coast

“…Farmlands and residential areas contribute to increased nutrient loading from fertilizers and septic systems. As an example, nutrient inputs due to human development may vary by five-fold across coastal watersheds in western Florida (Christiaen et al, 2016;Stutes et al, 2017). Canals also can contribute to saltwater intrusion and wetland loss (Penland et al, 2000).…”

“…Acidification, through enhanced carbonate dissolution and depressed carbonate precipitation, can affect the health of calcifying organisms (Lemasson et al, 2017), which are abundant in many areas of the Gulf Coast. Altered rainfall patterns through changes in the salinity of coastal 38 THE FUTURE OF THE U.S. GULF COAST PREPUBLICATION COPY: UNCORRECTED PROOFS waters, can cause large changes in coastal ecosystem structure (Christiaen et al, 2016). Increased frequency of extreme weather events, including major storms and hurricanes, may also alter substantially the dynamics of coastal ecosystems (Chen et al, 2017).…”

Canopy Functions of R. maritima and Z. marina in the Chesapeake Bay

“…Seagrasses are currently in decline due to decreased water quality and climate change (Cardoso et al, 2004;Orth et al, 2006), and beds in many areas could shift to being dominated by macroalgae or other seagrass species better able to cope with changing or degraded conditions (Armitage et al, 2011;van Tussenbroek et al, 2014). When a shift occurs between morphologically similar species, ecosystem functioning may not change (Christiaen et al, 2016), however, many co-occurring seagrasses have differing morphologies and life cycles. Several regions in the United States have experienced seagrass habitats transitioning from larger-form, spatially stable species to more opportunistic, smaller-form species (Fourqurean et al, 1995;Johnson et al, 2003;Bologna et al, 2007;Cho et al, 2009;Lopez-Calderon et al, 2010;Micheli et al, 2014).…”