Nearshore and offshore comparison of marine water quality variables measured during SESMA 1

Abstract

Total suspended solids (TSS), dissolved oxygen (DO) and dissolved inorganic nutrient concentrations [ammonium (NH4), nitrite (NO2), nitrate (NO3), phosphorus (PO4) and silicate (SiO4)] were measured in offshore sites covered by the first Scientific Expedition to the Straits of Malacca or SESMA 1 cruise. Both TSS and DO showed striking differences between nearshore and offshore sites. TSS was elevated nearshore (> 250 mg l-1) but was < 100 mg l-1 offshore. DO was at healthy levels (> 300 µM or 9.6 mg l-1) offshore but were low and sometimes exhibited hypoxia (< 125 µM or 4 mg l-1) nearshore. Dissolved inorganic nutrients were generally higher nearshore and this reflected eutrophication. High TSS, low DO and eutrophication showed that anthropogenic activities are affecting the marine water quality in Malaysia.
Dalam kajian ini, kami mengukur beberapa pembolehubah kualiti air marin di stesyen luar pantai semasa Ekspidisi Saintifik ke Selat Melaka atau pelayaran SESMA 1. Data yang diperolehi dibandingkan dengan stesyen dekat pantai. Jumlah ampaian pejal (TSS), oksigen larut (DO) dan kepekatan nutrien inorganik larut [amonium (NH4), nitrit (NO2), nitrat (NO3), fosforus (PO4) and silikat (SiO4)] diukur. Kedua-dua TSS dan DO menunjukkan perbezaan ketara antara stesyen dekat pantai dan luar pantai. TSS adalah tinggi dekat pantai (> 250 mg l-1) tetapi < 100 mg l-1 luar pantai. DO adalah pada tahap sihat (> 300 µM atau 9.6 mg l-1) luar pantai tetapi adalah rendah dan kadang kala mempamerkan hipoksia (< 125 µM atau 4 mg l-1) dekat pantai. Nutrien tak organik larut adalah pada amnya lebih tinggi dekat pantai dan ini mencerminkan eutrofikasi. TSS yang tinggi, DO yang rendah dan eutrofikasi menunjukkan bagaimana aktiviti antropogenik sedang memberi kesan terhadap kualiti air marin di Malaysia.