Seagrass consumption by native and a tropically associated fish species: potential impacts of the tropicalization of the northern Gulf of Mexico

Abstract

Temperatures are rising in most temperate and polar environments, and a welldocumented effect of this change is a poleward range shift by a wide variety of terrestrial and aquatic species. In the northern Gulf of Mexico (GOM), an increasing number of tropical species have recently become established among the extant warm-temperate fauna. These include a diversity of tropical fishes, manatees, green turtles, warm-water corals, and black mangroves. The impact of these species may be profound, primarily because temperate species are restricted from shifting northward by the North American land mass. Thus, as tropical species expand northward in the GOM, they must interact with the extant species and potentially compete for essential resources or become prey for each other. Here we focus on tropical immigrants capable of transforming the vast and highly productive seagrass systems of the northern GOM, emphasizing herbivorous parrotfishes and comparing their impact with endemic seagrass-resident fishes. Increased numbers of these herbivores (plus green turtles and manatees) would likely shift detritus-based food webs in seagrass meadows to webs dominated by direct consumption of seagrasses. We provide estimates of some expected consumption rates and effects of these tropically associated seagrass herbivores and predict that the consequences of the increased tropicalization of northern GOM seagrass meadows will be: substantially reduced standing crops and structural complexity of seagrass meadows; increased energy flux through grazing food webs; and a greatly reduced nursery role that will result in much smaller adult populations of those finfish and shellfish species that rely on seagrasses as nurseries.

Demographic, Taxonomic, and Genetic Characterization of the Snook Species Complex (Centropomus spp.) along the Leading Edge of Its Range in the Northwestern Gulf of Mexico

“…; Heck et al. ). In this context, perhaps the most parsimonious conclusion is that the northward expansion of snook species in Texas is driven by warming trends that are also likely to sustain this new distribution.…”

“…However, examination of the relationship between year and the mean latitude of catch demonstrated a clear range expansion of snook into northern latitudesareas where these species were only rarely observed prior to 2010. This range expansion has coincided with a warming climate and the development of tropical conditions in temperate and subtropical waters (Staten et al 2018), resulting in the range expansion of tropical marine fish species into temperate zones worldwide (e.g., Figueira and Booth 2010;Nakamura et al 2013;Verges et al 2014;Heck et al 2015). In this context, perhaps the most parsimonious conclusion is that the northward expansion of snook species in Texas is driven by warming trends that are also likely to sustain this new distribution.…”

Beyond just sea‐level rise: considering macroclimatic drivers within coastal wetland vulnerability assessments to climate change

“…In some ways, the ecological effects of altered temperature and rainfall regimes in coastal wetland ecosystems are analogous to the tropicalization and desertification processes that are occurring and predicted for some marine and terrestrial ecosystems, respectively, in response to climate change. In an ecological context, tropicalization is a term that has been most often used within marine ecosystems in reference to the poleward movement of tropical marine organisms (e.g., Bates et al, 2014;Verg es et al, 2014;Heck et al, 2015). Desertification is a term that has been most often used in terrestrial ecosystems in reference to the conversion of vegetated wetter-climate ecosystems (e.g., grasslands) to arid-like ecosystems with lower vegetation coverage (e.g., Schlesinger et al, 1990;Reynolds et al, 2007;Peters et al, 2015).…”

Sighting demographics of the West Indian manatee Trichechus manatus in the north-central Gulf of Mexico supported by citizen-sourced data

“…Recently, climateas sociated changes in species distribution patterns have been detected worldwide at increasing rates among diverse groups such as fish, phytoplankton, corals, mangroves, and manatees (Precht & Aronson 2004, Fodrie et al 2010, Edwards 2013, Kibler et al 2015. On the US northern Gulf of Mexico coast, sightings of the endangered West Indian manatee have in creased in number and into colder months (Fertl et al 2005, Pabody et al 2009, Heck et al 2015). This increase in sightings has corresponded with increased seasonal mean water temperatures in the northern Gulf of Mexico region (Fodrie et al 2010) and manatee po pulation growth in Florida during the past several decades (Powell & Rathbun 1984, Eberhardt & O'Shea 1995, Bonde & Lefebvre 1999, Runge et al 2004.…”