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Reef-dweling Christmas tree worms (Spirobranchus, Serpulidae, Polychaeta), on Porites Corals: Densities and age structure

Luthfi Oktiyas Muzaky, Isdianto Andik, Akbar Dzikrillah

Polish Journal of Ecology

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2023

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Vol. 71, nr 4

115--125

EN

The primary objective of this study was to investigate the densities and age structure of Christmas tree worms Spirobranchus sp. (Serpulidae, Polychaeta), on colonies of massive stony corals of the genus Porites, which have not been reported before in the region. Pulau Sempu, East Java, Indonesia. Pulau Sempu is a small island and also the sole remaining nature reserve within the region of. This small island is encompassed by shallow and narrow fringing reefs, characterized by a composition of algae and an occurrence of hard corals, specifically from genera Porites, Pocillopora, and Coelastrea (formerly known as Goniastrea). The majority of Porites specimens creating a narrow reef encompassing the island is colonized by boring polychaets known as the Christmas tree worms, Spirobranchus sp., which inhabit the interior of coral skeletons. Studies were carried out in two specific locations within the nature reserve Pulau Sempu, i.e., Watu Mejo and Waru-Waru. Two species: Spirobranchus corniculatus and Spirobranchus cruciger, have been identified dwelling on corals. Our findings indicated that the density of the worms residing in large Porites was 8.62 individuals/ m2 in Watu Mejo and 9.02 individuals/m2 in Waru-Waru. The age of the worms found on Pulau Sempu, as determined by operculum size, ranged between 14 and 22 years. Worm age differ among study sites with older individuals observed at Waru-Waru.

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Observation of Coral Reef and Macroalgae Competition in the Sempu Strait, Malang

Isdianto Andik, Kurniawan Andi, Wicaksono Agus Dwi, Marhaendra Quanta Nur Ihza, Putri Berlania Mahardika, Fathah Aulia Lanudia, Asadi Muhammad Arif, Luthfi Oktiyas Muzaky, Pratiwi Dwi Candra, Harahab Nuddin

Journal of Ecological Engineering

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2023

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Vol. 24, nr 10

174--184

EN

Competition for space between coral reefs and macroalgae has a significant impact on coral cover and, consequently, on the sustainability of coastal ecosystems. This study aimed to ascertain the Sempu Strait’s substrate coverage, dominant coral reef lifeform, coral-macroalgae competition, and water quality. The Underwater Photo Transect method and the CPCe software are used to monitor coral reefs. The condition of the approximately 11.5% of living corals was deemed to be substandard. The western portion of the Sempu Strait is dominated by encrusting, branching, and massive corals, whereas the eastern portion is dominated by Acropora corals. Temperature varied between 26 and 35 °C, salinity varied between 17 and 35 ppt, pH varied between 7 and 8, water clarity varied between 2.25 and 2.73 m, and dissolved oxygen varied between 6.28 and 6.71 mg/L. Competition between corals and macroalgae is observed at multiple stations, including Banyu Tawar, Waru-Waru, and WatuMeja. This phenomenon can be attributed to the presence of suitable substrates such as sand, rubble, and pebbles, as well as favorable seasonal conditions and water quality that promote the growth of macroalgae. Essentially, macroalgae grow more rapidly than corals, resulting in competition for growing space.

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Assessment of Community Structure of Macroinvertebrates, Coral Cover and Water Quality in Sempu Strait, Malang Regency, East Java

Isdianto Andik, Kurniawan Andi, Wicaksono Agus Dwi, Taufik Muhammad Zaidan, Putri Berlania Mahardika, Fathah Aulia Lanudia, Setyanto Arief, Luthfi Oktiyas Muzaky, Pratiwi Dwi Candra, Harahab Nuddin

Journal of Ecological Engineering

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2023

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Vol. 24, nr 12

99--111

EN

Due to the sensitivity of invertebrates to environmental changes, their presence can serve as an indicator of coral reef health and water quality. This study seeks to ascertain the abundance of invertebrates, the structure of the invertebrate community, and their relationship with coral cover and water quality parameters in the waters of Sempu Strait. The belt transect method and the underwater photo transect (UPT) are used to determine the abundance of invertebrates and coral cover, respectively. Temperature, pH, DO, salinity, and water clarity are measured for water quality. According to the study’s findings, seven of the nine invertebrate species were found. Between October 2021 and May 2022, seven of nine invertebrate biota categories, 733 species, and 606 species dominated by Diadema sea urchins were observed every two months. The invertebrate abundance ranged from 0.024 to 0.512. A low and imbalanced invertebrate diversity ranges from 0.078 to 0.493 (H’ < 1). The range of the equality index (E < 0.4) is between 0.04 and 0.22, indicating a low community index. There are three levels of dominance index values: low, medium, and high. Due to their abundance, Diadema sea urchins dominate the Sempu Strait, particularly near the Jetty Station with its port activity. Coverage of coral reefs varies between 6% and 21.3%, indicating low and damaged corals. The correlation between coral cover and invertebrate abundance is moderate in Banyu Tawar and Rumah Apung (0.480 to 0.490), whereas it is weak in Waru-Waru, Watu Meja, and Jetty (-0.037–0.225). The abundance of invertebrates has a weak link with values ranging from -0.037 to -0.283 for water clarity, temperature, salinity, DO, and pH, but it has a strong correlation with a value of 0.610 for current velocity. The environment, including human activities and water quality, has a significant impact on macroinvertebrate communities. Environmentally tolerant macroinvertebrates will outcompete the vulnerable ones.