Variability of the trophic state in a coastal reef system associated with submarine groundwater discharge in the Mexican Caribbean.

Submarine groundwater discharges (SGD) have been associated with important sources of nutrients between the land and oceans that can generate eutrophication conditions. This study aims to analyze the behavior of nitrogen and phosphorus using the mixing curve method, to examine the variation of the trophic state using the Karydis Index, and to evaluate the δN in benthic organisms to trace the origin of nitrogen in neap tide (November) and spring tide (January) in the Manatí Cenote, and Nohoch-Teek reef lagoon in the Mexican Caribbean. Nitrogen and phosphate enrichment was in the Manatí Cenote during neap and spring tides.

Growth and shell hardness of the apple snail Say, 1829, reared at three calcium concentrations.

The snail inhabits aquatic systems with high calcium concentration and it is important to food webs; unfortunately, its natural populations are decreasing due to overfishing and habitat destruction. Here we tested the effect of three water calcium concentrations on the growth and hardness of snail shells in triplicate recirculation culture systems for 12 weeks. In each culture, 100 juvenile snails were seeded at constant density and fed with balanced tilapia feed.