Salinity and temperature regulations on the genus Trichodesmium in Pombo Island national marine park environment, Central Maluku
Sem Likumahua*, Fismatman Ruli

Research Center for Deep Sea, National Research and Innovation Agency, Jakarta, Indonesia (Branch Office Jl. Y. Syaranamual, Guru-guru, Poka - Ambon, 97233)
*seml001[at]brin.go.id

Abstract

Genus Trichodesmium is a wide-spread planktonic cyanobacteria in the world ocean that has an ability to fix nitrogen (N) from the atmosphere in N-starved marine environments. Thus, the present of the genus in a marine environment plays an important role in sustaining marine life by providing key nutrient elements via biogeochemical cycles. The present study aims to investigate Trichodesmium dynamics and their responses to environmental drivers in a national marine park Pombo Island during the easterly monsoon. Phytoplankton samples were collected using a plankton net during a fortnightly-campaign scheme between June and August, during which sea surface temperature, salinity, nitrate, phosphate and water transparency were measured from seven stations. Trichodesmium^s filaments were recorded in all stations during the observation with high percentages of occurrences (ranged between 13% and 59%) of the total phytoplankton community. During the observation, low sea surface temperature and high salinity levels were recorded indicating that Banda Sea^s upwelling reached Pombo Island. The principal component analysis revealed that during the upwelling period, Trichodesmium abundances were positively correlated with increased salinity, yet inversely correlated with temperature (n = 42). Meanwhile, nutrient concentrations showed no impacts on the abundance. This study revealed that physical properties mainly governed dynamics of the genus during the southeast monsoon, during which nutrient was provided by upwelling. Further annual dynamics needs to be investigated in order to fully understand environmental regulations on the genus as well as on N fixing processes and nutrient cycles.

Keywords: Cyanobacteria, nitrogen, upwelling, Banda Sea, southeast monsoon

Topic: Marine Resources, and Conservation