Biodiversity of epiphytic periphyton in the leaves of the seagrass bed of Talawaan Bajo Estuary, North Sulawesi, Indonesia

Ogi NLIM, Herawati EY, Risjani Y, Mahmudi M. 2021. Biodiversity of epiphytic periphyton in the leaves of the seagrass bed of Talawaan Bajo Estuary, North Sulawesi, Indonesia. Biodiversitas 22: 4857-4864. This study aimed to analyze the diversity of epiphytic periphyton on the leaves of the seagrass bed of Talawaan Bajo estuary North Sulawesi Indonesia. The study was performed in three sampling points by using the line transect method with 50x50 cm2. The sampling points were located in front of the residential area, the mangrove forest, and in budo Cape. Seagrass and periphyton communities were analyzed for species density, relative frequency, diversity, evenness, and dominance index. Water quality and heavy metal Hg were also measured. The results showed that Cymodocea rotundata was the dominant seagrass based on species density and frequency distribution. Periphyton composition on the leaf of C. rotundata consisted of Bacillariophyceae (16 genera), Cyanophyceae (3 genera), Chlorophyceae (9 genera), Dinophyceae (1 genus), and Rhodophyceae (1 genus). The water quality, such as phosphate, current, nitrate, dissolved oxygen, and Hg content in the water, contributed to changing the environmental condition of Talawaan Bajo waters. Therefore, the efforts to manage coastal resource conservation in the Talawaan Bajo estuary require more concern from the government and stakeholders of Talawaan Bajo.

Stable Isotope Tracer Addition Reveals the Trophic Status of Benthic Infauna at an Intertidal Area Adjacent to a Seagrass Bed

Stable isotope tracer addition can enhance the isotopic differences of primary producers for a wider food-web resolution than the use of natural abundance stable isotopes (NASIs) alone, particularly in ecosystems where primary producers have similar NASI values. To investigate the food sources and the trophic status of benthic infauna in an intertidal area near a Halophila minor seagrass bed within inner Tai Tam Bay, Hong Kong, China, a 15N addition experiment was conducted, and the results were compared with those from NASI data. Only benthic microalgae (BMA) were labeled by applying 15N-enriched NH4Cl to the sediment daily for the first 7 days during a 21-day study. In contrast to the NASI results, Bayesian mixing models based on the isotope tracer experiment suggested a larger dietary contribution of BMA for nematode Daptonema sp. and copepods, whereas a higher reliance on phytoplankton and seagrass detritus was noted for polychaete Neanthes sp. However, both NASI and isotope tracer addition demonstrated that seagrass detritus was a major food source for nematode Spilophorella sp. The present isotope tracer experiment also revealed a contrasting result of the relatively lower contribution of meiofauna in the diets of carnivores/omnivores as compared to the results of NASIs. This finding suggested that the isotope values in these consumers may have not reached an equilibrium with the added isotope in the study period. Thus, there is a need for applying NASI coupled with isotope tracer addition in the investigation of ecosystems in which primary producers have similar isotope values, especially in ecosystems with lower tissue turnover rates, in order for a more accurate determination of dietary contribution and trophic status of consumers in the food-web study.

Seagrass Condition at Some Small Islands in The Taka Bonerate National Marine Park, South Sulawesi Indonesia

The assessment of seagrass bed condition in Indonesia still refers to the Decree of the State Minister for the Environment (KMNLH) no. 200 of 2004, which considers only one variable, namely the percentage of seagrass cover. To assess the seagrass beds condition to be more in-depth and meaningful, it is necessary to consider the addition of several variables, such as the biotic variables (seagrass species diversity including macroalgae and macro-benthos components) as well as the abiotic variables (reef flat areas and the substrate components). The purpose of this study is to determine the seagrass beds condition in several small islands in the Taka Bonerate National Marine Park by considering the additional analysis using both biotic and abiotic variables as mentioned above. The methodology used in this study is a combination of the use of the standard seagrass transect method, interpretation of satellite imagery related to the seagrass bottom habitat area, and its components on the reef flat of a particular island, as well as weighting and scoring based on those considered additional variables. By applying the criteria in the method, the seagrass bed conditions were then classified into three categories, namely seagrass in good, moderate, and unfavorable conditions, respectively. The results of the total score assessment on several small islands in Taka Bonerate Islands show that the seagrass bed in Latondu Besar Island is in good conditions with the highest score of (316) compared to Tarupa Besar, Jinato, Rajuni Kecil, and Tinabo Besar Islands with an average score of (173). The results of this study indicate that the assessment of seagrass conditions is more meaningful in terms of seagrass ecology than based on seagrass cover alone. However, this study requires a lot of validation for its application in assessing the condition of seagrass beds in other islands in Indonesia.

Distribution, Temporal Change, and Conservation Status of Tropical Seagrass Beds in Southeast Asia: 2000–2020

Although Southeast Asia is a hotspot of global seagrass diversity, there are considerable information gaps in the distribution of seagrass beds. Broad-scale seagrass distribution has not been updated in the global seagrass database by UNEP-WCMC since 2000, although studies on seagrasses have been undertaken intensively in each region. Here we analyze the recent distribution of tropical seagrass beds, their temporal changes, causes of decline and conservation status in Southeast Asia (plus southern mainland China, Taiwan and Ryukyu Island of Japan) using data collected after 2000. Based on the 195 literature published since 2000, we identified 1,259 point data and 1,461 polygon data showing the distribution of seagrass beds. A large discrepancy was found in the seagrass bed distribution between our updated data and the UNEP-WCMC database, mostly due to inaccurate and low resolution location information in the latter. Temporal changes in seagrass bed area analyzed for 68 sites in nine countries/regions demonstrated that more than 60% of seagrass beds declined at an average rate of 10.9% year–1, whereas 20% of beds increased at an average rate of 8.1% year–1, leading to an overall average decline of 4.7% year–1. Various types of human-induced threats were reported as causes for the decline, including coastal development, fisheries/aquaculture, and natural factors such as typhoons and tsunamis. The percentage of seagrass beds covered with existing marine protected areas (MPAs) varied greatly among countries/regions, from less than 1% in Brunei Darussalam and Singapore to 100% in southern Japan. However, the degree of conservation regulation was not sufficient even in regions with higher MPA coverage. The percentage of seagrass beds within EBSAs (Ecologically and Biologically Significant Area determined by the Convention of Biological Diversity) was higher than that within MPAs because EBSAs cover a greater area than MPAs. Therefore, designating EBSAs as legally effective MPAs can greatly improve the conservation status of seagrass beds in Southeast Asia.

Keterkaitan Megabentos yang Berasosiasi dengan Padang Lamun terhadap Karakteristik Lingkungan di Perairan Jepara

Seagrass bed are one of the ecosistems in shallow waters that can support the biodiversity of marine organisms. Megabenthos as benthic organisms that usually live in association in seagrass beds, have an important role in the food web in their habitat. This study aims to analyse the diversity of megabenthos associated with their habitat characteristics in seagrass waters in Bandengan, Teluk Awur and Panjang Island Jepara. This research was conducted using a descriptive field method, and megabenthos data collecting was carried out using the line transect method. Thr result showed that 158 individuals from 8 species of megabenthos were found (from 2 phyla: Echinodermata and Molluska) from three observation locations. Condition factors that influence the abundance and diversity of megabenthos are the substrat type and seagrass cover. Padang lamun sebagai salah satu ekosistem di perairan laut dangkal dapat menopang keanekaragaman hayati organisme laut. Megabentos yang termasuk dalam organisme bentik merupakan organisme yang biasa hidup berasosiasi di padang lamun, mempunyai peranan penting dalam jaring-jaring makanan di habitatnya. Penelitian ini bertujuan untuk menganalisa keanekaragaman megabentos dikaitkan dengan karakteristik habitatnya di perairan padang lamun di Bandengan, Teluk Awur dan Pulau Panjang Jepara. Penelitian ini dilakukan dengan metoda deskriptif lapangan, dan pengambilan data megabentos dilakukan dengan metoda line transek. Hasil pengamatan menunjukkan ditemukan 158 individu dari 8 spesies megabentos (dari 2 filum: Echinodermata dan Molluska) dari ketiga lokasi pengamatan. Faktor kondisi yang berpengaruh terhadap kelimpahan dan keanekaragaman megabentos adalah jenis substrat dasar dan tutupan lamun.

Efisiensi Teknik Sampling dalam Penentuan Indeks Keanekaragaman Polychaeta di Padang Lamun Pantai Sire, Lombok Utara

Padang lamun merupakan salah satu ekosistem yang berperan sebagai tempat tinggal, tempat mencari makan, tempat pembesaran dan daerah pemijahan bagi sejumlah besar biota asosiasinya, termasuk polychaeta. Selain mengambil manfaat dari tumbuhan lamun, polychaeta juga berperan terhadap kesuburan substrat lamun karena kemampuannya dalam menguraikan serasah dan meningkatkan kadar oksigen dalam sedimen melalui aktivitas bioturrbasi. Penelitian ini bertujuan untuk mengetahui indeks keanekaragaman polychaeta di padang lamun Pantai Sire, Lombok Utara menggunakan 2 (dua) teknik sampling yang berbeda. Pengamatan data lamun dilakukan menggunakan kuadran 50x50 cm2, dengan 3 (tiga) transek dimana masing-masing terdapat 10 titik pengamatan. Pengambilan sampel polychaeta dilakukan menggunakan alat Ekman Grab dan PVC sediment corer. Hasil penelitian menunjukkan bahwa terdapat 5 (lima) jenis lamun dan 17 famili polychaeta di perairan padang lamun Pantai Sire, dimana Capitellidae merupakan jenis dengan rerata kelimpahan tertinggi (1.046±32,34 - 1.430±37,82 individu/m2). Hasil uji-t menunjukkan bahwa perbedaan teknik sampling berpengaruh terhadap total kelimpahan polychaeta di padang lamun, dimana teknik sampling menggunakan PVC sediment corer memiliki hasil yang lebih optimal dibandingkan mengunakan Ekman Grab. Hal tersebut menandakan bahwa alat PVC sediment corer lebih efisien digunakan untuk pengambilan sampel polychaeta di lamun karena sesuai dengan karakteristik substrat lamun yang berpasir. Sedangkan alat Ekman Grab lebih baik digunakan pada substrat berlumpur dan pada perairan yang cenderung dalam. Seagrass bed is one of the ecosystems that act as a place to live, foraging for food, rearing and spawning areas for a large number of associated biota, including polychaeta. Apart from taking advantage of seagrass, polychaeta also plays a role in the fertility of seagrass substrate because of its ability to break down litter and increase oxygen levels in the sediment through bioturbation activity. This study aims to determine the diversity index of polychaeta in seagrass bed at Sire Beach, North Lombok using 2 different sampling techniques. Seagrass data observation was carried out using a 50x50 cm2 quadrant, with 3 transects, each of which had 10 observation points. Polychaeta samples were taken using the Ekman Grab and the PVC sediment corer. The results showed that there were 5 specieses of seagrass and 17 families of polychaeta in seagrass of the Sire Beach, where Capitellidae was the species with the highest average abundance (1,046 ± 32.34 - 1,430 ± 37.82 individuals / m2). The t-test result shows that the different sampling techniques have a correlation to the total abundance of polychaeta, where PVC sediment corer has more optimal results than using Ekman Grab. This indicates that the PVC sediment corer is more efficient to use for polychaeta sampling in seagrass because of its suitability to the characteristics of sandy seagrass substrate. Meanwhile, the Ekman Grab is better to use on muddy substrates and in a deep water.