Symbiodiniaceae density pattern in relation to colony morphology of scleractinian corals in Pulau Tioman and Pulau Bidong, Malaysia

A healthy coral reef is linked to the mutualistic relationship between scleractinian coral and the symbiotic Symbiodiniacea (SD). However, there is limited research on SD in Malaysia, despite its important role in reef-building coral. In this study, the SD density of scleractinian corals from the family Acroporidae was evaluated to (i) examine the pattern of SD density and (ii) comprehend the regulation of the SD density by the host. The mean SD density ranged between 0.46 ± 0.01 × 106 cell cm-2 and 2.98 ± 1.17 × 106 cell cm-2. It is hypothetically proven that the SD density differed significantly between genera and morphological factors such as colony surface area (CSA) and dry weight coral tissue per unit colony surface area (DWCT/CSA) were significantly correlated with the SD density. The results show that the significant variation in SD density among coral genera can be influenced by coral growth forms and tissue biomass. There was a significant relationship between SD density and CSA as well as DWCT/CSA. Coral genera with a wider CSA and lower DWCT/CSA such as Anacropora and Acropora with branching, digitate and tabulate growth forms contained lower SD density than massive, laminar, and encrusting such as Montipora and Astreopora which hold more DWCT/CSA at lower CSA, resulting in higher SD density. The findings provide valuable information on SD density in different types of corals from the southern part of the South China Sea and reveal the coral host’s SD regulation

Monitoring climate change effects on coral reefs using edge-based image segmentation

Coral reefs are valuable ecosystems that face vulnerability to climate change impacts. Underwater images often encounter noise from various factors, such as water turbidity, lighting conditions, attenuation, and scattering, which can complicate edge detection and segmentation processes, leading to inaccuracies. However, image processing techniques offer a viable solution to this issue. In this study, an edge-based segmentation approach is proposed that uses multiple contrast techniques to detect and quantify changes in coral reef imagery. The proposed approach effectively identifies changes in coral reef imagery, making it a valuable tool for monitoring climate change's effects on these ecosystems. Furthermore, high-resolution images at different time points and locations were collected, and then an edge-based segmentation approach was utilized to enhance the accuracy of edge detection and segmentation. Comparing the proposed method with traditional segmentation techniques showed a significant improvement in terms of segmentation precision. Subsequently, alterations in the structure and composition of coral reefs are observed, indicating the influence of climate change on these ecosystems. This research highlights the capabilities of image processing techniques using edge-based segmentation in monitoring coral reefs. It offers an effective and precise approach to detecting changes in coral reef images, thereby contributing to conservation endeavors

Improved Coral Reef Images Segmentation using Modified JSEG Algorithm

Underwater coral reef image segmentation suffers from various challenges due to various factors especially variation in illumination, different water turbidity, different water depth, variation in color, texture and shape of the coral reef species. In this paper, we modified an original automatic color image segmentation called JSEG to enable better coral reef segmentation process. The modification involves the substitution of General Lloyd Algorithm and agglomerative algorithm in the original JSEG version with the k-means algorithm. In addition, the newly modified JSEG algorithm process image in L*a*b color space to provide better processing of underwater image color property while k-means algorithm is used to segment the color within the specified cluster number. The experimental results showed that the modified JSEG algorithm could segment the coral reefs better than the original JSEG algorithm

Assessment of governance and ecological status of Terengganu Marine Park, Malaysia: toward marine spatial planning

Terengganu Marine Parks (TMP) is a 591.37 km2 marine protected area. TMP are popular tourist destinations that significantly generate revenue to the government and local businesses through tourism sector. However, the anthropogenic activities have contributed to TMP’s declining ecosystem health, particularly the coral reefs. Therefore, a sustainable ecosystem-based management is required to maintain the ecosystem. In this study, we identify issues related to the marine park’s governance, development on islands, tourist activities and coral health status in the TMP for assessing potential management strategy for conserving the ecosystem. The findings on management in TMP found that there is an overlapping in managing the marine park between the federal and state government. Unintegrated development to accommodate rising number of tourist and their activities in the marine parks are identified as the factors contributing towards degradation of the ecosystems. Relatively, reef areas close to these local pressures are in ‘poor’ condition, indicating that threats arising from the activities affecting the marine ecosystem. Hence, this study analyses the potentials in adopting Marine Spatial Planning (MSP) in the TMP for managing the conflict between user and the ecosystem. The Australian Great Barrier Reef Marine Park which applied the zoning of marine area is used as a benchmark to examine the best practices of MSP to govern the TMP. At present, we suggest using coral reef health status as an early alternative and best practice to provide different zoning criteria for strategic marine protected area (MPA) management for TMP

Physical characteristics and nutrients status off Pulau Besar, Malacca and Tanjung Tuan, Negeri Sembilan, Malaysia: A preliminary study

Degradation of coastal water quality is one of the major concern in the Malacca Strait since this area is one of the most important fishing ground in Malaysia. Despite being great in the fishery industry, Malacca and Negeri Sembilan somehow recorded the lowest marine fishes landing, which raises a question about dynamics of this area. It is therefore, a preliminary study of the physical properties and nutrient concentrations carried out from 27 March to 4 April 2016 at the coastal water off the southern west coast of Peninsular Malaysia, specifically at Pulau Besar, Malacca and Tanjung Tuan, Negeri Sembilan. Data for temperature, salinity, and dissolved oxygen (DO) was acquired by using Conductivity, Temperature, and Depth (CTD) probe. Meanwhile, nutrient concentrations determination in this study was done by using a Westco Smartchem 200 Discrete Analyser, according to the procedure adopted from United States Environmental Protection Agency (USEPA). In general, results of this study indicated the coastal stations were characterised with cooler, less saline, and high DO waters than stations away from coast. Large sea surface heating and weak winds were determined as the causative factors affecting dynamics of water column at the study area. At nearshore area, temperature, salinity, and DO variability were modulated by degree of freshwater intrusion. High nutrient concentrations at the stations closer to the coast was believed to be associated with river outflow, which acted as the main source of nutrients supply in this area. Comparison to previous study had shown that nutrient concentrations in this research were low, which could contribute to an insight on declining marine fish catches in these two states. With regard to Malaysian Marine Water Quality Criteria and Standard (MWQCS), mean nutrient concentrations at the study area were in Class 1, which are suitable for marine parks and marine protected areas conservation. Regardless of limited scope, the outcome of this study is believed to be a good baseline reference for future studies seeking to understand coastal dynamics.The authors wish to acknowledge contributions and support from the staffs of INOS and SEAFDEC and financial support provided by SEAFDEC (ESI 67920)

Coral Reef Mapping of UAV: A Comparison of Sun Glint Correction Methods

Although methods were proposed for eliminating sun glint effects from airborne and satellite images over coral reef environments, a method was not proposed previously for unmanned aerial vehicle (UAV) image data. De-glinting in UAV image analysis may improve coral distribution mapping accuracy result compared with an uncorrected image classification technique. The objective of this research was to determine accuracy of coral reef habitat classification maps based on glint correction methods proposed by Lyzenga et al., Joyce, Hedley et al., and Goodman et al. The UAV imagery collected from the coral-dominated Pulau Bidong (Peninsular Malaysia) on 20 April 2016 was analyzed in this study. Images were pre-processed with the following two strategies: Strategy-1 was the glint removal technique applied to the whole image, while Strategy-2 used only the regions impacted by glint instead of the whole image. Accuracy measures for the glint corrected images showed that the method proposed by Lyzenga et al. following Strategy-2 could eliminate glints over the branching coral—Acropora (BC), tabulate coral—Acropora + Montipora (TC), patch coral (PC), coral rubble (R), and sand (S) with greater accuracy than the other four methods using Strategy-1. Tested in two different coral environments (Site-1: Pantai Pasir Cina and Site-2: Pantai Vietnam), the glint-removed UAV imagery produced reliable maps of coral habitat distribution with finer details. The proposed strategies can potentially be used to remove glint from UAV imagery and may improve usability of glint-affected imagery, for analyzing spatiotemporal changes of coral habitats from multi-temporal UAV imagery

Multispecific synchronous coral spawning on Pulau Bidong, Malaysia, South China Sea

[Extract] Multispecific synchronous spawning appears to be a feature of all speciose coral assemblages (Guest et al. 2005) having now been reported from at least 25 locations in the Indo-Pacific (Baird et al. 2015). Nonetheless, there are many aspects of coral spawning that remain poorly understood, and many regions for which there is little data. In particular, there are few records of coral spawning from the South China Sea. Information on the timing of coral spawning is also important for the effective management of human activities such as coastal development (Baird et al. 2011). Here, we document multispecific synchronous spawning of scleractinian corals on Pulau Bidong (5°37´N, 103°03´E), an inshore island on the east coast of Peninsular Malaysia

Effects of tourism-derived sewage on coral reefs: Isotopic assessments identify effective bioindicators

Pulau Redang and Pulau Tioman have experienced huge tourism growth over the last two decades, but minimal sewage treatment may threaten the resilience of their coral reefs. This study uses stable isotope techniques to identify suitable bioindicators of sewage nutrients (δ15N) at these islands by measuring macroalgae (Lobophora spp.), gastropods (Drupella spp.), scleractinian coral (Acropora spp.), and leather coral (Sinularia spp.). At tourist hubs using seepage septic tank systems, enrichment of Acropora δ15N (Redang, +0.7‰) and Sinularia δ15N (Tioman, +0.4‰) compared to pristine background levels indicate enhanced sewage nutrient discharge. Carbon isotopes and survey data suggest that sedimentation did not confound these δ15N trends. Potential damaging effects of sewage discharge on the coral reef communities at both islands are highlighted by strong correlations between Acropora δ15N and regional variation in coral reef community structure, and exclusive occurrence of degraded reefs at regions of high sewage influence