DISSOLVED SILICATE IN COASTAL WATER OF SOUTH SULAWESI
<p><strong><em>ABSTRACT</em></strong></p> <p><em>Dissolved silicate (DSi) in coastal waters plays a crucial role in phytoplankton</em><em> </em><em>growth particularly diatom</em><em>.</em><em> This study aimed to </em><em>determine</em><em> DSi</em><em> </em><em> concentration </em><em>seasonally </em><em>in waters of the western coast of South Sulawesi in relation to coastal water quality</em><em> indicator. Water, c</em><em>hlorophyll-a</em><em>,</em><em> and diatom samples were collected </em><em>from</em><em> the coastal areas of the Tallo-Makassar, Maros, and Pangkep, in April 2013 (transitional season), June 2013 (dry season), and February 2014 (wet season). Factorial analysis of variance was used to identify significant seasonal and temporal variations, and linear regression was used to test the relationship of chlorophyll-a and diatom abundance to DSi concentrations. The results showed that the DSi concentration was higher in the wet season </em><em>of</em><em> 35.2</em><em>-</em><em>85.2 µM than in the other seasons (transitional season: 10.8</em><em>-</em><em>68.4 µM, dry season: 9.59</em><em>-</em><em>24.1 µM). The abundance of diatoms during the transitional season reached ~9.7x10<sup>7</sup> cell/m<sup>3</sup> in the Pangkep river, 2.3x10<sup>7</sup> cell/m<sup>3</sup> in the Tallo river, and 1.3 x 10<sup>7</sup> cell/m<sup>3</sup> in the Maros river. <span style="text-decoration: underline;">Chaetoceros,</span> <span style="text-decoration: underline;">Nitzschia</span>, and <span style="text-decoration: underline;">Rhizosolenia </span>dominated the diatom composition. The mean concentration of chlorophyll-a in the Makassar coastal waters was 4.52±4.66 mg/m<sup>3</sup></em><em>, </em><em>while in the Maros </em><em>and Pangkep </em><em>waters </em><em>of</em><em> 1.40±1.06</em><em>, and </em><em>2.72±1.94 mg/m<sup>3</sup>,</em><em> respectively.</em><em> There was no strong linear corelation between DSi and diatom abundances, nor chlorophyll-a. These results suggest</em><em>ed</em><em> that DSi become a non-limiting factor for the </em><em>diatom </em><em>growth </em><em>and potentially reduce the water quality via</em><em> eutrophication and diatom blooms. </em></p> <p><strong> </strong></p> <strong><em>Keywords: </em></strong><em>dissolved silicate, diatom, chlorophyll-a, coastal waters, South Sulawesi</em>