Resumen de Application of Landscape Ecology to Spatial Variance of Water-Quality Parameters Along the Florida Keys Reef Tract

D. Wagner, E. Mielbrecht, Robert van Woesik

• Since large-scale spatial differences in temperature and salinity influence the global distribution of coral reefs, it seems reasonable to assume that local differences may also influence community assemblage rules. Yet, we do not understand the spatial and temporal scales at which many water quality parameters vary. This study examined the spatial variance of ten water quality parameters along the Florida Keys reef tract using landscape ecology techniques, coupled with geographic Information System (GIS) technologies. Temperature, salinity, chlorophyll a, and dissolved inorganic nitrogen (DIN) were spatially predictable at the scale of the sampling design (km). Near-substrate temperatures were homogeneous at patches <= 1.075 km, while surface temperatures were homogenous at patches <= 0.893 km. DIN patches were more homogeneous near the substrate (<= 2.873 km) than at the surface (0.151 km), with surface chlorophyll a homogeneous at <= 0.592 km. In contrast, salinity at the surface was more homogeneous (<= 1.662 km) than near the substrate (<= 0.234 km). Other nutrient parameters, including ammonium (NH4), nitrate (NO3), total nitrogen (TN) and total organic nitrogen (TON), and turbidity were not predictable at the spatial scale at which the parameters were sampled, and therefore did not capture the inherent scale at which these parameters varied. Differences between surface and near-substrate temperatures increased significantly as depth increased, suggesting that satellite-derived sea surface temperatures may be overestimating temperatures at which corals bleach.