Kwee Siong Tew

A long-term survey on anthropogenic impacts to the water quality of coral reefs, southern Taiwan

Before 2001, the ecological protection area in the Kenting National Park (KTNP), southern Taiwan, was poorly described. In this study, a set of four-year data (2001-2004) of seawater qualities at 19 sampling sites around the Nanwan Bay in the KTNP was used to explore anthropogenic impacts to ecological environment, especially coral reefs. The parameters of water quality were analyzed immediately after collection. The results showed that higher values of nutrients and suspended solids were attributed to the higher run-off around Nanwan Bay. The fluxes of nutrients and suspended solids were consistently correlated to rainfall. Hence, equations were developed to calculate nutrient fluxes and suspended solids by using only rainfall data. Our results show that suspended solids and ammonia were the dominant factors leading to the drop in coral coverage. In summary, the water quality in the intertidal zone of Nanwan Bay has been degraded and required greater attention.

Analysis of the coral associated bacterial community structures in healthy and diseased corals from off-shore of southern Taiwan

The methods of denaturing gradient gel electrophoresis (DGGE) and DNA sequencing were used to analyze the ribotypes of microbial communities associated with corals. Both healthy and diseased coral of different species were collected at three locations off the southern coast of Taiwan. Ribotyping results suggested that the microbial communities were diverse. The microbial community profiles, even among the same species of corals from different geographical locations, differ significantly. The coral-associated bacterial communities contain many bacteria common to the habitants of various invertebrates. However, some bacteria were unexpected. The presence of some unusual species, such as Staphylococcus, Clostridium and Legionella, associated with corals that were likely the results of human activities. Human activities, such as thermal pollution from the nearby nuclear plant, active fishing and tourism industries in the region might have all contributed to the change in bacterial communities and the death of coral colonies around the region.

Physiological and biochemical performances of menthol-induced aposymbiotic corals.

The unique mutualism between corals and their photosynthetic zooxanthellae (Symbiodinium spp.) is the driving force behind functional assemblages of coral reefs. However, the respective roles of hosts and Symbiodinium in this endosymbiotic association, particularly in response to environmental challenges (e.g., high sea surface temperatures), remain unsettled. One of the key obstacles is to produce and maintain aposymbiotic coral hosts for experimental purposes. In this study, a simple and gentle protocol to generate aposymbiotic coral hosts (Isopora palifera and Stylophora pistillata) was developed using repeated incubation in menthol/artificial seawater (ASW) medium under light and in ASW in darkness, which depleted more than 99% of Symbiodinium from the host within 4∼8 days. As indicated by the respiration rate, energy metabolism (by malate dehydrogenase activity), and nitrogen metabolism (by glutamate dehydrogenase activity and profiles of free amino acids), the physiological and biochemical performances of the menthol-induced aposymbiotic corals were comparable to their symbiotic counterparts without nutrient supplementation (e.g., for Stylophora) or with a nutrient supplement containing glycerol, vitamins, and a host mimic of free amino acid mixture (e.g., for Isopora). Differences in biochemical responses to menthol-induced bleaching between Stylophora and Isopora were attributed to the former digesting Symbiodinium rather than expelling the algae live as found in the latter species. Our studies showed that menthol could successfully bleach corals and provided aposymbiotic corals for further exploration of coral-alga symbioses.

Environmental influence on coastal phytoplankton and zooplankton diversity: a multivariate statistical model analysis

In a marine ecosystem, the diversity of phytoplankton can influence the diversity of zooplankton, or vice versa, and both can be affected by the environmental factors. In this study, we used principal component analysis (PCA) to identify the major sources of influence on the coastal water near an industrial park, following by construction of structural equation model (SEM) to determine the direct and indirect effect of the factors on phytoplankton and zooplankton diversity. PCA results indicated that the coastal area was mainly affected by riverine discharge (represented by high PC factor loadings of transparency and turbidity) and seasonal change (represented by temperature). SEM further suggested that both riverine discharge and seasonal influences can directly affect phytoplankton diversity, but indirectly affected zooplankton diversity via changes in phytoplankton. Using PCA to determine the sources of influence followed by construction of SEM allowed us to understand the relative importance of the environmental factors, direct or indirect, on phytoplankton and zooplankton diversity. When environmental changes occur, a new SEM could be constructed using the same category of physical and biological data and then compared to the current model to verify whether the environmental changes were the cause of alterations in planktonic communities in the area.

Kinetics of polychlorinated biphenyl partitioning to marine Chrysophyte Isochrysis galbana.

This study focused on the uptake kinetics of polychlorinated biphenyl (PCB) congeners by the Chrysophyte, Isochrysis galbana. A gas-purging experimental system was used to maintain constant dissolved PCB concentrations. Three phases of absorption were observed: first, a rapid absorption phase within the first 15min, second, a first order process reaching the maximum concentration within 48h of exposure, and third, a plateau phase as yet to be determined with very slight increases in concentration. In this study, the percentage of the maximum concentration reached within the first phase varied from 10% to 67%, depending on the size of the PCB (as determined by molecular weight and total surface area), whereas the uptake rate (k(u)) during the second phase was more comparable across different PCBs. In addition, for the first phase, the bioconcentration factor (BCF) of PCBs deviated from its expected relationship with hydrophobicity, as determined by K(ow), and was instead related to the molecular structure of the compound.

Comparison of the decapod communities in an anthropogenic impacted lagoon and its adjacent coastal waters

In this study, benthic decapods were sampled approximately for every three months between September 2000 and June 2002 in a heavily used subtropical lagoon and its vicinity waters in southwestern Taiwan. Seventeen shrimp species (dominated by Metapenaeus ensis and Penaeus semisulcatus) and 19 crab species (dominated by Thalamita crenata) were recorded within the lagoon, whereas a combined total of 32 shrimp species (mainly Metapenaeopsis barbata and M. palmensis) and 50 crab species (dominated by Portunus hastatoides) were recorded at 10, 20, 30, and 40-m depths outside the inlet–outlet of the lagoon. The decapod community in the lagoon varied little temporally, and was significantly different from those in the nearby waters. The results of this study document a decapod fauna in a lagoon subjected to decades of aquaculture activities and revealed that these activities benefited a distinct decapod assemblage, yet may have prevented the potential use of the lagoon by other species as a nursery or refuge. Aquaculture activities have since been prevented and dredging of the benthic sediments in the lagoon has been underway; thus the results of present study will provide a valuable and rare baseline data set to be used for future studies to determine how decapod communities shift in response to habitat change.

A continuous, real-time water quality monitoring system for the coral reef ecosystems of Nanwan Bay, Southern Taiwan.

The coral reef ecosystems of Nanwan Bay, Southern Taiwan are undergoing degradation due to anthropogenic impacts, and as such have resulted in a decline in coral cover. As a first step in preventing the continual degradation of these coral reef environments, it is important to understand how changes in water quality affect these ecosystems on a fine-tuned timescale. To this end, a real-time water quality monitoring system was implemented in Nanwan Bay in 2010. We found that natural events, such as cold water intrusion due to upwelling, tended to elicit temporal shifts in coral spawning between 2010 and 2011. In addition, Degree Heating Weeks (DHWs), a commonly utilized predictor of coral bleaching, were 0.92 and 0.59 in summer 2010 and 2011, respectively. Though this quantity of DHW was below the presumed stress-inducing value for these reefs, a rise in DHWs in the future may stress the resident corals.

The importance of phosphorus and copper carryover in pond sediments for juvenile percid survival, growth, and yield.

Abstract Over-fertilization with phosphorus and carryover copper residual in the sediment from copper sulfate treatment in double-cropped ponds were suspected as the primary causes of low larval percid survival in coolwater aquaculture ponds. Consequently, in this study, we compared saugeye (male sauger Sander canadensis × female walleye S. vitreus) survival, growth, and yield among ponds that were single-cropped with only saugeyes in the spring during the previous two consecutive years (SS ponds) and ponds that were double-cropped (with saugeye culture in the spring and channel catfish Ictalurus punctatus culture in the summer) during the previous two consecutive years (DD ponds). We also compared sediment phosphorus (soluble reactive phosphorus [SRP] and total phosphorus [TP]), sediment copper concentrations, phytoplankton biomass, and zooplankton biomass. Fish survival (number harvested) and fish yield (mass harvested) were significantly lower in DD ponds than in SS ponds in 2001 but were similar in 20...

Effect of a rainfall pulse on phytoplankton bloom succession in a hyper-eutrophic subtropical lagoon

In the present study, we sought to understand the succession of phytoplankton species, after a natural nutrient pulse, in a subtropical lagoon located in southern Taiwan. The lagoon was surrounded by aquaculture ponds. The present study was performed during the wet summer season, before and after an episode of heavy precipitation. Before rainfall commenced, both the phosphate concentration and the level of phytoplankton were relatively low. After heavy precipitation, physical and chemical measurements indicated that significant amounts of dissolved inorganic nutrients had drained into the lagoon. A phytoplankton bloom occurred; organism levels reached 77.6×105 cells L–1. The dominant organism was Chaetoceros curvisetus (99.3%). After the bloom ceased, the levels of inorganic nutrients, especially silicate, fell. Phytoplankton became of low abundance once more. At the end of our study period, the ecosystem was dominated once more by diatoms (75.8%); this may have been caused by a low-level nutrient pulse following rainfall that occurred one day before final sampling. Overall, our results suggest that the bloom succession of phytoplankton species was principally dependent on nutrient dynamics in the lagoon, which was associated with nutrients discharged from drainage after heavy rainfall.

Characterising and predicting algal blooms in a subtropical coastal lagoon

Algal bloom is a major concern worldwide. In this study, we characterised the physical and biochemical parameters during an algal bloom event in a coastal lagoon in an attempt to predict local blooms in the future. Results showed that the highest concentrations of dissolved inorganic phosphorus (DIP), chlorophyll a (chl a) and phytoplankton abundance were found in the inner area, whereas the highest dissolved inorganic nitrogen (DIN) concentration occurred near the inlet-outlet channel. Chl a was correlated with DIP, and there was a significant exponential relationship between chl a and the nitrogen to phosphorus ratio (N/P ratio) across all sampling stations and times. A higher proportion of the variation in chl a was explained by the N/P ratio than either DIP or DIN. We found that a N/P ratio <2.38 will likely trigger an algal bloom (chl a ≥ 10 µgL–1) in the lagoon. Our results suggest that the N/P ratio could be used as an expedient and reliable measure of the potential eutrophic status of coastal lagoons.