Influence of several stressful factors on the condition of seagrasses at Sabana–Camagüey​ Archipelago, Cuba

Abstract

The influence of three potential anthropogenic stressful factors (coastal pollution from the mainland, the causeway Caibarién–Santa María and fishing with bottom-trawling nets) on the condition of seagrasses was assessed at 12 sites in two bays of Sabana–Camagüey​ archipelago, between 2010 and 2013. As for indicators of the condition of the seagrass ecosystem, the structure of the macrophyte community, marine angiosperm’s shoot density, and shoot length of marine angiosperms were analyzed. Abiotic variables as depth, turbidity, temperature, pH, dissolved oxygen, oxygen saturation, and chemical oxygen demand of seawater, were evaluated. The relationships of the three potential anthropogenic stressful factors and the abiotic factors (predictor variables) with the biological response variables were analyzed. Seagrass meadows in better condition, with higher values of cover and density of Thalassia testudinum, and lower values of depth, turbidity, salinity, chemical oxygen demand, were found at sites out of the bays and furthermost from the causeway and mainland. Areas without vegetation or with lower values of cover and density of T. testudinum, and higher cover of macroalgae and pioneer species of marine angiosperms as Syringodium filiforme and Halodule wrightii, were found in both bays. Turbidity and depth were the abiotic factors with the stronger negative influence on the structure of the seagrass community. Chemical oxygen demand and salinity also showed negative influences. Coastal pollution seems to be the anthropogenic factor that most influences the condition of seagrasses. No recovery of seagrasses was observed in areas where bottom-trawling fisheries had ceased. Distance to the causeway was not correlated with the condition of seagrass, but the potential for a negative influence on circulation persists. Seagrasses in the studied bays remain affected by the above-mentioned predictor abiotic factors, whose effects may be reinforced by the three anthropogenic stressful factors, acting synergistically with the bays’ oceanographic characteristics.