Malaysian Journal of Analytical Sciences Vol 23 No 6 (2019): 1030 - 1043

DISTRIBUTION OF NUTRIENTS CONCENTRATION IN THE UPWELLING AREA OFF THE EAST COAST OF PENINSULAR MALAYSIA DURING THE SOUTHWEST MONSOON

(Taburan Kepekatan Nutrien di Kawasan Julang Air di Pantai Timur Semenanjung Malaysia Semasa Monsun Barat Daya)

Azyyati Abdul Aziz¹_, Suhaimi Suratman^1,2*, Poh Heng Kok¹, Mohd Fadzil Akhir¹

¹Institute of Oceanography and Environment

²Institute of Tropical Biodiversity and Sustainable Development

Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia

*Corresponding author: miman@umt.edu.my

Received: 30 October 2018; Accepted: 26 September 2019

Abstract

An oceanographic survey was conducted with RV Discovery at the east coast of Peninsular Malaysia (ECPM) (i.e. Kelantan and Terengganu) facing the South China Sea during the southwest monsoon in July 2017, to understand the variations in the distribution of phosphate, silicate, dissolved organic carbon (DOC), and chlorophyll-a (chl-a) in response to coastal upwelling events. Seawater samples were collected from five transects, consisting of 27 sampling stations within the area from 4.0ºN - 6.5ºN and 102.3ºE - 106.0ºE. The data collection was organized into horizontal and vertical distributions. Physico-chemical parameters like temperature and salinity were also studied. We found that the horizontal distribution of phosphate and chl-a was significantly higher in the coastal area as compared to the offshore area. An irregular distribution pattern of DOC and silicate was also observed. Additionally, higher concentrations of phosphate, silicate, DOC and chl-a were observed at the northern area (nearby Gulf of Thailand) as compared to the southern area. It is possible that the northern area received a high input of nutrients from the Gulf of Thailand. Generally, the vertical distributions of nutrients show a tendency to be lower in surface water areas and increase towards deep water areas. An upwelling event was observed in Terengganu waters as a sudden decrease in temperature (from 29.85 to 24.89 ºC) was found at 4.0ºN -5.0ºN here, as compared to other areas in the ECPM. The results from this study can be used in comparisons as there is no baseline of nutrient concentrations available for this area at the moment.

Keyword: phosphate, silicate, dissolved organic carbon, upwelling, vertical and horizontal distribution, southwest monsoon

Abstrak

Kajian oseanografi telah dijalankan dengan RV Discovery di Pantai Timur Semenanjung Malaysia (ECPM) (iaitu Kelantan dan Terengganu) yang menghadap ke Laut China Selatan semasa monsun barat daya pada bulan Julai 2017 untuk memahami taburan variasi fosfat, silikat, karbon organik terlarut (DOC) dan klorofil-a (chl-a) yang bertindak balas terhadap julang air pantai. Sampel-sampel air laut diambil dari lima transek yang terdiri daripada 27 stesen pensampelan yang merangkumi kawasan dari 4.0 - 6.5 ºN dan 102.3 -106.0 ºE. Himpunan data telah disusun secara taburan mendatar dan menegak. Parameter fiziko-kimia seperti suhu dan saliniti turut dikaji. Kami mendapati taburan mendatar fosfat dan klorofil-a adalah secara signifikan lebih tinggi di kawasan pantai berbanding kawasan luar pesisir, dan diperhatikan corak taburan tidak teratur untuk DOC dan silikat. Di samping itu, kepekatan fosfat, silikat, DOC dan chl-a adalah tinggi di kawasan utara (berhampiran Teluk Thailand) berbanding dengan kawasan selatan. Adalah kemungkinan kawasan utara menerima kemasukan nutrien yang tinggi dari Teluk Thailand. Umumnya, taburan nutrien di permukaan air secara menegak menunjukkan kecenderungan untuk menurun dan meningkat ke arah air dalam. Julang air diperhatikan di perairan Terengganu apabila terdapatnya penurunan suhu secara mendadak (dari 29.85 hingga 24.89 ºC) yang ditemui di 4.0-5.0 ºN berbanding dengan kawasan lain di ECPM. Hasil dari kajian ini boleh digunakan sebagai perbandingan kerana setakat ini tiada kepekatan dasar mengenai nutrien di kawasan ini.

Kata kunci: fosfat, silikat, karbon organik terlarut, julang air, taburan menegak dan mendatar, monsun barat daya

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