New Insight Into the Mechanism of Ecological Effects of Artificial Habitats: Elucidating the Relationship Between Protists Associated With Artificial Reefs and Adjacent Seawater

Artificial habitat deployment can restore natural habitats or supplement existing natural habitats. The effect of resource proliferation and protection is obvious. However, few reports have addressed the biological community association between artificial habitats and adjacent environments. Here, Illumina sequencing of 18S rDNA was performed, and the diversity, community structure, and co-occurrence networks of protists in different layers of artificial reefs (ARs) and adjacent seawater (WAR) were described to verify that constructing ARs in Bailong Pearl Bay improves local spatial heterogeneity and functional diversity. In terms of the degree of species interaction, the protist communities were ranked as follows: surface and bottom of WAR > ARs and WAR > different layers of ARs. The α-diversity of protists associated with ARs and WAR decreased with an increase in depth. Protist diversity was greater in WAR than in ARs. β-Diversity analysis revealed significant differences in protist community structure between WAR and ARs (P < 0.05), and the upper layers of ARs and the middle or bottom layers of ARs differed. The key topological features of protist networks showed more positive interspecific interactions in the AR-associated protist community, a higher degree of niche differentiation, and higher complexity and stability. The keystone protists in the bottom seawater layer displayed community functions that were biased toward initial fixation in the ocean carbon cycle. The AR-associated protist community tended to participate in carbon transfer in the food chain and decomposition and utilization of dissolved organic matter (DOM). This study revealed significant differences in protist community structure between ARs and the adjacent environment, and the ecological functions of the key phyla were found to be related. In conclusion, protist communities in WAR may provide food sources for AR-associated heterotrophic protists. A variety of key phyla associated with ARs have biological roles in the carbon pump via their ecological characteristics.

Improving Biological Reefing Viability Index as a Predictive Tool for Assessment of Potential Reefing Site in the Tropical Shallow Offshore Environment

The current study improved the predictive capability of the biological reefing viability index (BRVI) calibrated using local data. The prediction capability of the BRVI improved from 61% to 76% accuracy out of the 181 locations where the underwater videos available for verification. The BRVI includes corals larvae density, age of larvae at site, sea current, sea temperature, chlorophyll-a, water depth and sediment type to predict biological productivity of an area. Among the parameters, corals larvae density and age of the larvae are the most critical parameters that influent establishment of new biological ecosystem. The BRVI uses settlement of corals larvae as the precursors for the establishment of new habitats in the offshore environment because scleractinian corals is known to be able to form backbone of a new habitat in the environment. In this approach, the BRVI focuses on habitat creation instead of just being a fish aggregating device (FAD) when an artificial reef is deployed in an area. The BRVI can be used as a rapid screening tool to identified potential area for deployment of artificial reefs. The BRVI could reduce the chances of artificial reefs deployment that failed to address its objectives and intended outcomes.

Diversity of Benthic Organisms on Artificial Reef Structure

One of the methods of a marine rehabilitation program to accelerate the recovery of damaged coral reefs is to make artificial reefs as a new coral growth substrate. Interestingly, many benthic invertebrates overgrowth the artificial reef structures. The purpose of this study was to investigate the benthic organisms encrusting the artificial reefs including the cement and iron substrates. In June 2018, 10 artificial reef structures were deployed in 7-8m depth around Putri Island, Belinyu, Bangka Regency. The artificial reef structures were made in the form of an iron frame with a cement concrete weight. Colonization of sessile benthic organisms is generally marine invertebrates; Scleractinia corals, sponges, bivalves, hydrozoa, bryozoa, soft corals, gastropoda, crinoid, ascidian, and gorgonian. Natural recruited coral Pocillopora sp. was found in all artificial reef structures with colony sizes 3-8cm and surprisingly only coral pocillopora found adhered in iron frames and sinkers. The other benthic organisms are sponge, crinoid, and bryozoa with the number of densities are 2 organism/m2. Meanwhile, the lowest benthic density are groups of Mollusc and Ascidian with organism/m2. The type of succession that occurs in this research was likely a primary succession. The preference of benthic organisms among reefs appeared to be related to the proximity of natural hard-bottom habitat and type of iron and coating materials.