ALONG THE UPPER TEXAS COAST SPATIAL AND TEMPORAL DISTRIBUTIONS OF PLANKTONIC DIATOMS IN A SUBTROPICAL BAYOU

A study of planktonic diatom (Bacillariophyceae) community spatial and temporal distributions was carried out in Offatts Bayou, a small embayment within the larger Galveston Bay complex in southeast Texas. The dominant diatom genera were Chaetoceros, Ditylum, Rhizosolenia, Coscinodiscus, Guinardia, Dactyliosolen, Odontella and Lithodesmium, in this order. Over 20 other diatom genera were represented at different times including some known to produce toxins (e.g., Pseudonitzschia), while others only appeared in surface waters after strong wind induced mixing events (e.g., Navicula). The spatial and temporal patterns observed for the dominant planktonic diatoms followed changes in salinity and temperature. Other environmental variables (light, nutrients, grazing) were not measured as part of this initial investigation but may have been important. Mean Chaetoceros, Ditylum, Odontella and Lithodesmium standing crops were highest at the open end of the bayou, while Guinardia and Dactyliosolen numbers were highest in the most flow-restricted regions of the bayou. Spatial distributions of Rhizosolenia and Coscinodiscus were homogenous throughout Offatts Bayou. Understanding natural diatom succession patterns may provide important insights into normal variations in community composition. Diatoms are potentially a powerful biomonitoring tool for future assessments of the impacts of eutrophication, climate change and/or human induced ecosystem dysfunction.

SPATIAL AND TEMPORAL DISTRIBUTIONS OF PLANKTONIC DIATOMS IN A SUBTROPICAL BAYOU, ALONG THE UPPER TEXAS COAST Academic Article