Influence of temperature on the occurrence and distribution of the sand shrimp Crangon septemspinosaSay, 1818 (Decapoda: Caridea: Crangonidae) in polyhaline lagoons in Maryland, USA

Sand shrimp, Crangon septemspinosaSay, 1818, is one of the most abundant decapod crustaceans in estuaries and coastal waters of the northwestern Atlantic Ocean, though little is known about its population dynamics in polyhaline lagoons of the mid-Atlantic region. Seasonal and spatial patterns of abundance and distribution of C. septemspinosa were evaluated in relation to temperature, salinity, and dissolved oxygen in Maryland coastal bays (MCBs) using monthly data (April to October 1994 to 2012). We tested the hypothesis that temperature influences the occurrence and distribution of sand shrimp in the lagoons. A consistent pattern of high relative abundance of shrimp in spring and its scarcity in summer and early fall was observed. Shrimp abundance was highest in the northern bays and at sites closest to the Ocean City Inlet during April, but lowest at sites in the upper parts of Chincoteague Bay and MCBs tributaries. As mean temperature increased from April (12.2–17.1 oC) to June (21.8–26.7 oC), the relative abundance of the shrimp decreased substantially at most sites except at two sites where mean water temperature was comparatively low (21.8–23.3 oC). By July, when mean temperature was at its maximum (23.1–28.9 oC) in the bays, shrimp were rarely caught in trawls even in early fall in spite of the decline in temperature. It is likely that shrimp moved into nearshore waters with cooler temperature or suffered high mortality due to high temperature during this period. Generalized linear models suggest that temperature, and temperature and dissolved oxygen combined, were the most important abiotic factors examined that influenced the spatial distribution of C. septemspinosa in May and June, respectively. Considering their trophic importance, the spatio-temporal variations in the occurrence and abundance of the shrimp have implications for food web dynamics in the MCBs.

The Foraminifera of Chincoteague Bay, Assateague Island, and the Surrounding Areas: a Regional Distribution Study

Foraminiferal census data from Chincoteague Bay, Newport Bay, the salt marshes of Assateague Island, adjacent mainland salt marshes, and the inner-shelf, were assessed to determine the current assemblages in Chincoteague Bay, and how the different environments surrounding the bay, and the gradients within the bay, influence the microfossil distribution. Determining the current background distribution and its drivers allows for future comparisons to determine paleoenvironmental conditions, impacts from natural and anthropogenic pollution, and the influence of climate change. Foraminiferal census data were compared to sedimentological characteristics and environmental parameters, exhibiting strong correlations with salinity, sediment organic content, and grain-size. Foraminiferal distributions exhibited a gradient from an assemblage dominated by Elphidium cf. E. excavatum near Chincoteague inlet to an assemblage dominated by Ammonia parkinsoniana and Ammobaculites cf. Ab. exiguus in the more restricted central and northern portions of the bay. The sites closest to the mouth of Trappe Creek in Newport Bay, along the western side of Chincoteague Bay and in the central bay, had a greater relative abundance of dead agglutinated taxa compared with the majority of sites in Chincoteague Bay. Despite the overwhelming dominance of calcareous taxa throughout the bay, dissolution may affect the preservation potential of Cribroelphidium poeyanum and Haynesina germanica in the northern and central portions of Chincoteague Bay, as indicated by seasonal pH data. Similarly, the sandy back-barrier lagoonal sites exhibited relatively low densities, potentially a result of dissolution or mechanical destruction.