Malaysian Journal of Analytical Sciences Vol 23 No 6 (2019): 1090 - 1106

TEMPORAL VARIABILITY OF PHYTOPLANKTON BIOMASS IN RELATION TO SALINITY AND NUTRIENTS IN A SHALLOW COASTAL LAGOON

(Kepelbagaian Temporal Biojisim Fitoplankton Berdasarkan Kemasinan dan Nutrien di Lagun Pesisir Pantai yang Cetek)

Zuraini Zainol and Mohd Fadzil Akhir*

Institute of Oceanography and Environment,

Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia.

*Corresponding author: mfadzil@umt.edu.my

Received: 30 October 2018; Accepted: 26 September 2019

Abstract

With agriculture and aquaculture activities in proximity, the unique feature of Setiu Lagoon, which is an almost closed system and connected to the coastal sea with only one inlet leaves a huge question on how this ecosystem maintains its productivity under restricted conditions. In this study, results of three field samplings carried out during the southwest monsoon (August 2017), wet period of northeast monsoon (December 2017), and dry period of northeast monsoon (February 2018) are used to examine the differences in phytoplankton biomass in relation to salinity and nutrients under different monsoonal settings. These samplings are representative of typical conditions existing during a dry season (southwest monsoon) and a rainy one (northeast monsoon). In the lagoon, the most determinant factor affecting the phytoplankton biomass distribution is the freshwater intrusion, strengthened by increased rainfall amount and strong flow that brings along nutrients from land resulting in higher chlorophyll a concentrations. As per classification of Malaysia Marine Water Quality Criteria and Standard (MWQCS), mean nutrient concentrations at the study area were in Classes 1 and 2, which are suitable for local aquaculture activities. However, conservation actions must also be in line with the economic development.

Keywords: salinity, tidal, freshwater intrusion, nutrients, chlorophyll a, shallow coastal lagoon

Abstrak

Dengan dikelilingi dengan aktiviti akuakultur dan pertanian di kawasan terdekat, persekitaran unik Lagun Setiu - yang merupakan sebuah sistem yang hampir tertutup dan hanya mempunyai satu muara yang menghubungkan lagun dengan laut - meninggalkan satu persoalan yang besar tentang bagaimanakah ekosistem ini mengekalkan produktiviti dalam keadaan yang terbatas. Dalam kajian ini, hasil kajian melalui tiga pensampelan lapangan yang dijalankan sewaktu monsun barat daya (Ogos 2017), musim hujan monsun timur laut (Disember 2017), dan musim kering monsun timur laut (Februari 2018) digunakan untuk mengkaji perubahan biojisim fitoplankton berdasarkan kemasinan dan nutrien di bawah pengaruh monsun yang berbeza. Pensampelan ini mewakili keadaan biasa yang wujud semasa musim kering (monsun barat daya) dan musim hujan (monsun timur laut). Di dalam lagun ini, kemasukan air tawar yang dipengaruhi oleh pertambahan air hujan dan nutrien dari daratan yang dibawa oleh aliran air yang kuat merupakan faktor yang paling mempengaruhi penghasilan biojisim fitoplankton yang tinggi. Merujuk kepada Kriteria dan Piawaian Kualiti Air Marin, Malaysia (MWQCS), purata kepekatan nutrien di kawasan kajian berada di dalam Kelas 1 dan 2, yang sesuai untuk aktiviti akuakultur tempatan. Walaubagaimanapun, usaha pemuliharaan juga haruslah seiring dengan perkembangan ekonomi.

Kata kunci: kemasinan, pasang surut, kemasukan air tawar, nutrien, klorofil a, lagun pesisir pantai yang cetek

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