Case study of phytoplankton blooms in serangoon harbor of Singapore

Abstract

A recent algal bloom in the East Johor Strait has led to the damage of marine life in the water channel. This has lead to heavy economic losses to the fish farms located along the water channel. There is a desire to study and be able to predict the occurrences of algal blooms so that their effects on the fish industry can be reduced. Many factors such as weather patterns, tidal conditions and nutrient content in the water contribute to the extent of the eutrophication. This paper describes the design of experiments carried out in the East Johor Strait to study the dynamics of algal blooms. Physical and biogeochemical water column sampling were carried out using Acoustic Doppler Current Profilers (AD-CP) and a Conductivity, Temperature and Depth (CTD) probe that could measure various water quality parameters such as Turbidity, Salinity, pH level, Dissolved Oxygen (DO) and Chrolophyll-a concentration. Water samples from 1 m below the surface and 1 m above the channel floor were collected using Niskin Bottles. The water samples were sent to chemistry labs to test for the concentrations of various nutrients such as Ammonium, Nitrite, Nitrate and Phosphorus. Additional sampling was done using an Autonomous Underwater Vehicle (AUV) that was capable of measuring water quality parameters similiar to those measured by the CTD. The collection of the water sample data were meant to coincide with the spring and neap tides. The schedule is important to align with major phases of astronomic tide driving forces, such as flood tide, ebb tide and the transition between the two. Comparison can then be made to attempt to understand the various factors that contribute to algal blooms in the water body. Collected biogeochemical data can be used to improve water quality forecasts as well.

Frequent pulse disturbances influence resistance and resilience in tropical marine microbial communities

“…As the increase in N compared to P or Si also results in an increase in microbial biomass, we suggest that nitrogen is the limiting nutrient in preventing the over-proliferation of photosynthetic microorganisms. This has also been mentioned in past studies 10, 12 .…”

“…As mentioned in the sections above, water mixing in the Johor Strait is primarily driven by tides (Figure S4). Previous studies have also concluded that blooms happen more frequently during neap tides when tidal mixing is at its minimum, due to the higher cell densities during a stable water column 10,12 . However, we propose that stratification during minimum tidal mixing may also prevent the predators (grazers, viruses) from reaching their target preys.…”

“…However, despite the almost constantly eutrophic conditions, there seems to be some sort of stability in the Johor Strait microbial community as the water does not experience blooms every day. While many observational studies on both bloom and baseline conditions have been conducted in the recent years, none of these studies were done from the perspective of disturbance/resilience of a microbial community despite mentioning some of these disturbances (e.g., sporadic and sudden changes in nutrient inputs and salinity) 3, 5, 6, 10, 12, 13 . Moreover, as the Johor Strait is influence more by short-term environmental changes rather than seasonal ones8, the aforementioned studies were not conducted in a high enough temporal resolution to see the influences of the multitude of pulse disturbances on the microbial community of the Johor Strait.…”

“…No natural microbial community is immune to changes in environmental conditions, and the microbial communities of the inner Johor Strait are no exception. The Johor Strait is home to many open cage fish farms, and seasonal harmful algal blooms (HABs) have occurred in these waters which had caused billions of dollars in losses to the aquaculture industry [9][10][11][12][13][14] . However, despite the almost constantly eutrophic conditions, there seems to be some sort of stability in the Johor Strait microbial community as the water does not experience blooms every day.…”

Spatial Distribution Trend of Plankton in Sungai Pulai Estuary, the Straits of Johor, Malaysia

“…The co-occurrence would also imply the mixing condition of open and coastal water in the estuary . O'boyle and Silke (2010) and Ooi et al (2010) showed the role of tides in controlling the algal abundance in Singapore water. The condition might be important to maintain the composition of plankton species in the Sungai Pulai estuary.…”