ECOLOGICAL ANALYSIS IN A POLLUTED AREA OF ALGECIRAS BAY (SOUTHERN SPAIN) - EXTERNAL (VERSUS INTERNAL OUTFALLS AND ENVIRONMENTAL IMPLICATIONS

The effects of organic effluents both inside and outside the Saladillo Harbour (Algeciras, southern Spain) are investigated. Although the ex ternal outfall has a greater rate of discharge, the low levels of hydr odynamism inside the harbour create an area of relatively stagnant wat er, with markedly different environmental conditions. A clear gradient of decreasing pollution levels was observed from the interior to the exterior of the harbour. This was reflected both in the physicochemica l water and sediment parameters and in their respective microbiologica l parameters. Macrobenthic species also mirrored the pollution gradien t, as did the applied analysis, The effects of the external outfall ar e seen to dissipate and clear much closer to the external pollution so urce than in the internal, enclosed harbour area. (C) 1997 Elsevier Sc ience Ltd.