Komodo National Park is one of the favorite destinations for both domestic and international marine tourism. Marine tourism activities have caused environmental changes and impact on fisheries and marine resources. Macroalgae were also affected by the environmental changes, so management of macroalgae was required. Ecological data of macroalgae can be used as baseline data for coastal area management. The study aimed to determine the life form, species composition, spatial distribution, and ecological aspects of macroalgae assemblages in Komodo National Park waters. The study was conducted in September 2013, in eight locations, namely Setuga, Komodo Karang Makasar, Padar Kecil, Padar, Papagarang, Mangaitan, and Muntia island. Macroalgae samples were collected by the quadratic transect method. The data analyzed were Sorensen’s similarities. A total of 42 species of macroalgae were recorded, consisting of three Phylum: Chlorophyta (19 species), Ochrophyta (8 species), and Rhodophyta (15 species). Epilithic was the dominant life form of macroalgae. In general, macroalgae can be stably attached to hard substrates. The highest macroalgae diversity was found on Mangaitan Island (22 species). Halimeda and Amphiroa were macroalgae that can be found in almost all locations. Setuga Island had similar macroalgae with both Mangaitan and Muntia islands. The differences in the number of macroalgae species were influenced by environmental pressure, topography, and substrate profile. Management of macroalgae resources was needed to maintain the sustainability of the macroalgae ecosystem.

Anthropogenic activities will lead to an exponential increase in CO2 emissions in the future. Increased CO2 emissions have an impact on global climate patterns, ocean acidification, and ecosystem function. Marine vegetation has the potential to absorb CO2 through photosynthesis and store carbon in its biomass and sediments. This is known as blue carbon. Research on blue carbon in the world, including Indonesia, is more focused on seagrass and mangroves because including macroalgae carbon in the blue carbon strategy is still controversial. Currently, there are many considerations for including macroalgal carbon in the blue carbon strategy. Macroalgae have a shorter life cycle than seagrass and mangroves. In addition, macroalgae generally grow on hard substrates, resulting in lower levels of carbon storage than seagrass and mangroves. However, macroalgae can serve as carbon donors and contribute to the effort to mitigate climate change. In this review, we present the potential and challenges of macroalgae as carbon donors. Macroalgae will be significant as carbon donors if they have the following three criteria: high production of biomass; effective biomass moved to recipient habitat; and carbon donors that can be buried in recipient habitat. The fate of macroalgae carbon in recipient habitats still needs to be studied.

Juvenile corals are an important stage in the life history and demographics of coral populations in nature however, their survival is influenced by the physical environment and benthic coral reef communities. The study of juvenile coral communities with a maximum size of 10 cm on the reefs of Pulau Weh, Sabang, Aceh was conducted to observe juvenile coral communities and determine their relationship with geomorphological types and benthic reefs communities. A total of 9 sites with 72 sampling squares were distributed in different geomorphological; tectonic type with hard substrates of lava and limestone, volcanic type with predominantly sand substrate, and dead coral with algae with the presence of hot springs in the vicinity. In total, we found 25 genera of juvenile corals from 12 families, and the abundance reached 449 colonies with an average of 37.41 colonies per site. The mean density was 6.66 ± 5.99 colonies/m2 (±SD) and varied significantly between sites (p=4.878-7; <0.05), which was dominated by the genera Porites, Pavona, Acropora, Montipora, and Favia. Live coral cover (HC), dead coral algae (DCA), and hard rock substrate (RK) did not affect, however rubble coral (R) was significantly affected (p=1.9-2; <0.05). Geomorphological conditions and benthic reef cover did not show a significant effect (p = 0.48; < 0.05), although juvenile corals were very common and better in the tectonic type than the volcanic type. The survival of juvenile corals was low, where the smaller size was significantly high compared to the larger size (p=4.5-5; <0.05). Our study provides up-to-date information and data on juvenile coral communities based on geomorphological conditions and local benthic reef communities.