Multiple stressors threaten the imperiled coastal foundation species eelgrass (Zostera marina) in Chesapeake Bay,USA

Abstract

Interactions among global change stressors and their effects at large scales are often proposed, but seldom evaluated. This situation is primarily due to lack of comprehensive, sufficiently long-term, and spatially extensive datasets. Seagrasses, which provide nursery habitat, improve water quality, and constitute a globally important carbon sink, are among the most vulnerable habitats on the planet. Here, we unite 31 years of high-resolution aerial monitoring and water quality data to elucidate the patterns and drivers of eelgrass (Zostera marina) abundance in Chesapeake Bay, USA, one of the largest and most valuable estuaries in the world, with an unparalleled history of regulatory efforts. We show that eelgrass area has declined 29% in total since 1991, with wide-ranging and severe ecological and economic consequences. We go on to identify an interaction between decreasing water clarity and warming temperatures as the primary drivers of this trend. Declining clarity has gradually reduced eelgrass cover the past two decades, primarily in deeper beds where light is already limiting. In shallow beds, however, reduced visibility exacerbates the physiological stress of acute warming, leading to recent instances of decline approaching 80%. While degraded water quality has long been known to influence underwater grasses worldwide, we demonstrate a clear and rapidly emerging interaction with climate change. We highlight the urgent need to integrate a broader perspective into local water quality management, in the Chesapeake Bay and in the many other coastal systems facing similar stressors.

Heat‐stress induced flowering can be a potential adaptive response to ocean warming for the iconic seagrass Posidonia oceanica

“…They have developed adaptive strategies for living totally submerged in seawater (Olsen et al, 2016;Wissler et al, 2011), modifying important reproductive and life history traits including sexual reproduction, through submerged flowers, filamentous pollen and hydrophilous pollination (Du & Wang, 2014;Philbrick & Les, 1996). Recent summer heatwaves have impacted seagrass ecosystems, causing in some cases massive plants die-off (Lefcheck, Wilcox, Murphy, Marion, & Orth, 2017;Moore, Shields, & Parrish, 2014;Pagès et al, 2017;Thomson et al, 2015). The negative impact of ongoing climate change is expected to increase in the near future, with severe ecological and economic consequences given the numerous ecological functions and socio-economical services that seagrass ecosystems provide (e.g., Nordlund, Koch, Barbier, & Creed, 2016) and which render them one of the most valuable ecosystems on earth (Costanza et al, 2014).…”

Impact of multiple stressors on juvenile fish in estuaries of the northeast Pacific

“…Stressors to coasts and estuaries can take many forms, including shoreline urbanization, pollution, reduced water flows, and eutrophication (Airoldi & Beck, 2007;Greene, Blackhart, Nohner, Candelmo, & Nelson, 2015;Kennish, 2002;USEPA, 2012). Although stressors can be documented directly, significant effort is required to quantitatively compare them to the condition of species, especially given interactions among multiple stressors (Kroeker et al, 2016;Lefcheck, Wilcox, Murphy, Marion, & Orth, 2017;Vasconcelos et al, 2007). The management implications of this are real, both in developing methods to control escalating stressors, and in determining the ongoing consequences of these stressors on protected fisheries species (Kappel, 2005).…”

Impacts of predators, habitat, recruitment, and disease on soft-shell clamsMya arenariaand stout razor clamsTagelus plebeiusin Chesapeake Bay

“…The availability of some refuge habitats, such as seagrass and oyster shell, is decreasing 105 in the Chesapeake Bay (Rothschild et al 1994, Lefcheck et al 2017). The severe and persistent 106 declines of Chesapeake Bay seagrass in the recent past have been attributed mostly to 107 anthropogenic nutrient and sediment pollution, which decrease water clarity (Kemp et al 2004).…”

“…The dominant seagrass species in Chesapeake Bay, eelgrass Zostera marina, is also sensitive to 109 warming, and the interaction between warming and poor water quality has resulted in recent 110 declines of shallow beds (Lefcheck et al 2017). In the past several years, seagrass die-offs 111 induced by extreme high temperatures in Chesapeake Bay have resulted in the prediction that Z.…”