Effects of Lagoon-Ocean Connectivity on the Structure of Juvenile Fish Assemblages

The marine environment heavily influences the physical and biotic structure of lagoonal estuaries. That juvenile fish assemblages in coastal lagoons often reflect those found in adjacent nearshore ocean waters suggests that the ocean serves as a source pool for recruits. To investigate the fine-scale impact of the nearshore ocean on fish assemblage within a coastal lagoon system, both Maryland coastal bays and adjacent ocean waters (connected by a single inlet) were intensively sampled in summer and fall 2009. Assemblages differed significantly between the coastal bays and nearshore ocean in both seasons, but did not significantly differ between regional lagoons. Despite lacking lagoonal differences, assemblage within the coastal bays changed in a serial manner with increasing distance from the ocean. The nearshore ocean did not exhibit a similar effect, suggesting inputs from the ocean may cause an ecocline in bay assemblage structure, but not vice versa. Carbon stable isotope analysis of fish tissue reinforced the possibility of time-stable serial assemblage progression from the ocean. As a result of stable lagoon-marine connectivity, fine- to large-scale impacts on species within the associated nearshore ocean may influence assemblage structure within the coastal bays.