RESULTS OF EXPLORATORY CORING IN LAGUNA LAKE, PHILIPPINES

Laguna Lake is a large lake in the central Philippines, close to Metro Manila. Agricultural, industrial and urban development is expanding r apidly in the Laguna Lake basin, giving rise to many forms of environm ental stress in the lake and surrounding watershed. In particular, the lake appears to be subject to high rates of sedimentation, and the yi elds of both open lake and captive fisheries have severely declined. E xploratory coring was undertaken to provide a better understanding of lake sedimentation and long term trends in lake productivity. Actual r ates of sedimentation are thought to be about 1-1.5 cm y-1 and are lik ely about half the calculated rate (unadjusted for sediment mixing). T rends in diatom content and surrogate data (including loss on ignition ) suggest major variations which may correlate with changes in product ivity and food-web structures.