Temperatures are increasing globally and causing species-specific geographic range expansions. In the Gulf of Mexico, mangroves are encroaching regions historically dominated by temperate salt marshes, changing animal communities and nutrient cycling in the intertidal zone. Marine systems are highly connected; therefore, we expect that changes in the intertidal will alter functions of adjacent subtidal seagrass meadows. We surveyed seagrass meadows adjacent to mangroves, salt marshes, and a mixture of the two and asked, do changes in intertidal plant composition influence (1) environmental conditions (subtidal water and sediment characteristics); (2) biogeochemical cycling (net oxygen and nitrogen gas fluxes); (3) seagrass meadow cover, biomass, and productivity; and (4) invertebrate community assemblage? There are clear differences in sediment organic matter and net nitrogen gas (N₂) fluxes between adjacent intertidal habitats, but the magnitude or direction of change differs seasonally. We hypothesize that this seasonal pattern is due to outwelling from the intertidal, as mangroves senesce in fall, and marshes senesce later in winter. Therefore, changes in adjacent intertidal habitat can impact the timing of organic matter delivery. This also has implications for seagrass biomass. Thalassia testudinum belowground biomass adjacent to mangroves substantially decreased over the winter, suggesting vulnerability to stressors as the intertidal plant community shifts from marsh to mangrove dominance. Epifauna density and diversity did not vary among seagrass meadows based on adjacent intertidal habitats, but subtle differences in community assemblages associated with shifts in intertidal plant community were detected. This work demonstrates that impacts of species range expansions are far-reaching due to connectivity in marine systems.

全球温度正在上升，并导致特定物种的地理范围扩大。在墨西哥湾，红树林一直侵占着温带盐沼，不断变化的动物群落和潮间带养分循环的地区。海洋系统高度连接；因此，我们希望潮间带的变化将改变相邻潮间带海草草甸的功能。我们调查了与红树林，盐沼以及两者的混合物相邻的海草草甸，并询问潮间带植物组成的变化是否会影响（1）环境条件（潮间带水和沉积物特征）；（2）生物地球化学循环（氧气和氮气净流量）；（3）海草草甸覆盖率，生物量和生产力；（4）无脊椎动物群落？沉积物有机质和净氮气（N₂）相邻潮间带生境之间的通量，但变化的幅度或方向随季节而变化。我们推测，这种季节性模式是由于潮间带的潮汐所致，因为红树林在秋天衰老，而在冬天晚些时候变成沼泽。因此，相邻潮间带栖息地的变化会影响有机物的输送时间。这也对海草生物量具有影响。睾丸草在冬季，与红树林相邻的地下生物量显着减少，这表明随着潮间带植物群落从沼泽转移到红树林优势地位，对压力源的脆弱性。根据相邻的潮间带生境，海草草甸的浮游动物密度和多样性没有变化，但是发现与潮间带植物群落的变化有关的群落组合的细微差异。这项工作表明，由于海洋系统的连通性，物种范围扩大的影响是深远的。