11
DEC
2017

Variasi Nutrien dan Kelimpahan Fitoplankton dengan Pasang Surut Semasa Musim Berbeza di Tanah Bencah Setiu

Name: Nur Hafizah binti Merzuki
Course: Master of Science (Marine Sciences)

Satu kajian mengenai perubahan nutrien dan kelimpahan fitoplankton dengan air pasang surut pada musim yang berbeza di tanah bencah Setiu telah dijalankan semasa peralihan monsun (September dan Oktober 2012) dan Timur Laut (NE) (Februari dan Disember 2013) musim tengkujuh. Tiga stesen pensampelan telah dipilih untuk kajian ini. Stesen 1 dan 2 yang terletak di perairan laut dan payau, manakala stesen 3 terletak di kawasan air tawar. Kemasinan dan nilai suhu adalah rendah semasa air pasang purnanma pada musim tengkujuh, kerana aliran masuk air tawar yang besar dari hujan lebat. Di samping itu, awan besar-besaran dalam tempoh musim tengkujuh mengurangkan keamatan cahaya dari matahari. Kepekatan yang lebih tinggi nutrien iaitu ammonia dan nitrat telah direkodkan semasa musim tengkujuh yang mungkin disebabkan oleh air larian dari tanah ke kawasan tanah lembap dan ini adalah lebih ketara pada air pasang purnama. Kepadatan fitoplankton lebih tinggi dicatat pada air pasang perbani pada musim tengkujih. Secara umum, kumpulan filum Bacillariophyta didapati paling dominan fitoplankton pada semua peristiwa. Korelasi Canonical Analysis (CCA) menunjukkan korelasi positif antara parameter alam sekitar dan fitoplankton. Kebanyakan parameter menunjukkan hubungan yang positif dengan fitoplankton marin di stesen 1 dan 2. Station 3 menunjukkan korelasi negatif yang kuat dengan kemasinan sebagai fitoplankton adalah daripada genus air tawar. Perubahan nutrien dan komuniti fitoplankton adalah mungkin disebabkan oleh kesan kitaran pasang surut pada air pasang purnama dan air pasang perbani. Nutrien adalah dianggap salah satu parameter penting yang mempengaruhi pertumbuhan komuniti fitoplankton. Oleh itu, struktur masyarakat fitoplankton di tanah bencah Setiu didapati dipengaruhi mengikut adanya dan kepekatan nutrien yang terjejas oleh kitaran pasang surut dan musim.

 

Figure 1

Figure 2
Figure 1: (a) CCA showing scatter plot for all seasons against environmental variables at all station during spring and neap tide cycle in Intermonsoon; (b) CCA showing scatter plot for phytoplankton species against environmental variables at all station during spring spring-neap tide cycle in Intermonsoon, (c) CCA showing scatter plot for all seasons against environmental variables at all station during spring and neap tide cycle in NE monsoon; (d) CCA showing scatter plot for phytoplankton species against environmental variables at all station during spring-neap tide cycle in NE monsoon season. Spring tide= (ST), neap tide = (NP);

 

Canonical correlation analysis (CCA) was applied to explore variables of physic-chemical parameter between phytoplankton genus groups throughout the study period. The results shows in Figure 1 (a, b, c and d) revealed that season and tidal cycle affected the environmental condition and changed the phytoplankton assemblages. Changes in genus composition and diversity may affect phytoplankton growth rate and those parameters regulating the photosynthetic response to irradiance or other limiting factors. The tidal cycle and seasonal changes directly affect the nutrients concentration in water of Setiu Wetland. This was indicated by the changes in physical water parameters, phytoplankton abundance and species composition of according to seasons.

 

The phytoplankton composition was found being effected by the seasonal changed. During intermonsoon, marine phytoplankton obviously dominating the area with Bacillariphyta as major represented. However, freshwater phytoplankton density surprisingly increases with the decreasing of salinity during NE monsoon. The environmental factors change will directly affect the composition of phytoplankton. It is because different genus phytoplankton favours different of factors for growth. Bacillariophyta maintain as a most dominating phylum for all the result presented, corresponding with high number of genus present throughout the study period even within the changes of abundance in each sampling time. Physico-chemical variables collectively varied across the four sampling periods although this was not necessarily evident when considering the variables independently. Density and diversity of phytoplankton also varied with the changing season.