Band 63, Heft 5

With the potential adverse effects of climate change, it is essential to enhance the understanding of marine ecosystem dynamics, which can be driven by the co-evolutionary interaction between autotrophs and herbivores. This study looked into the autotroph-herbivore interactions in Malaysian waters, mainly to determine if autotroph nutritional quality significantly influences herbivore consumption rates. We documented the relative consumption rate of a generalist herbivore ( Chanos chanos Forsskål) obtained from the Straits of Malacca through multiple feeding trials using 12 macroalgal species collected from different coastal areas of the Straits of Malacca, the Straits of Johor, and the South China Sea. The herbivore fed selectively on the tested macroalgal species, with the most and least consumed species having the lowest and highest total nitrogen content, respectively. Besides total nitrogen content, the least consumed species also had the highest total phenolic content. Interestingly, we observed that the herbivore generally preferred to consume filamentous macroalgae, especially those collected from the South China Sea. Overall, our findings demonstrated that the feeding behaviour of a generalist herbivore could be influenced by the nutritional quality of the autotrophs, which may depend directly or indirectly on other factors such as autotroph morphology and geography.

The inter-specific resilience among mangrove species to sea level rise (SLR) is a key to design conservation strategies for this economically important ecosystem that is among the most vulnerable to SLR. Tectonic processes can cause sudden increases or drops in sea level due to subsidence or uplift of the land surface, which can also provide insights for the mangrove community responses to rapid sea level change. This study aimed to investigate the responses of mangrove species to rapid SLR caused by land subsidence of 1.1 m during the 2004 Sumatra-Andaman earthquake at Car Nicobar Island. The Rhizophora spp. showed remarkable resilience to this rapid SLR, while the landward mangrove vegetation comprising Bruguiera spp., Lumnitzera spp., Sonneratia spp. etc., were unable to survive. Also, Rhizophora spp. establishment in the previous landward mangrove zones was more rapid than the landward mangrove species establishment in the previous terrestrial zones. The observed resilience of Rhizophora spp. may be due to the local specific geological legacy and species-specific ecological processes. However, further studies focusing on microcosm experiments to understand the Rhizophora spp. resilience to rapid SLR at the study site is required to strengthen these observations.

Seagrass conservation and management requires scientific understanding of spatial and temporal variability, information that is currently limited for the Eastern Tropical Pacific (ETP). Here, we analysed seagrass presence based on previous reports, herbarium collections and stakeholder knowledge, combined with field characterization in Golfo Dulce, southern Pacific coast of Costa Rica. Seagrasses were found at multiple locations along a narrow border close to shore and in up to 6 m depth within Golfo Dulce, dating back to 1969. Two seagrass species were found, Halophila baillonii and Halodule beaudettei. Seagrass biomass values for Golfo Dulce (12.0 ± 8.5 g DW m −2 ) were lower and water nutrient concentrations were higher than previously reported in the gulf. Shoot density (1513 ± 767 shoots m −2 ) was similar to previous reports. Stable isotope values in seagrass were −11.3 ± 1.0‰ δ 13 C and 1.2 ± 0.9‰ δ 15 N; while those in sediments were −26.1 ± 1.3 and 2.5 ± 0.9‰. In Golfo Dulce, isotopic values of both seagrass species do not overlap with other known primary producers. Management strategies should aim to minimize known seagrass stressors, protect potential seagrass habitat, and take into account the dynamic life strategies of the two seagrass species found.

The marine algal flora of eastern Sorsogon has been intensively collected and is generally considered as the richest in the Philippines. A trend of species records in the area has been dominated by rhodophytes (red algae) with significantly fewer similar studies for other algal groups (green and brown algae). In this study we present an updated catalogue of the green seaweeds (Ulvophyceae) of eastern Sorsogon. A checklist, including notes on taxonomy, is given of the 103 species. Twenty-six species are newly recorded locally of which five represent new records for the Philippines: Avrainvillea amadelpha , Caulerpa buginensis, an unidentified Caulerpa species, Codium cf. latum , and one taxon new to science. The new species is described as Halimeda magnicuneata Verbruggen et Dumilag based on morpho-anatomy and DNA sequence data. The number of ulvophycean species recorded in eastern Sorsogon is found to be the highest in the Philippines. This may be a result of the high collection effort in the region, as well as eastern Sorsogon’s diverse habitats providing favourable conditions for a wide range of seaweed species.

Three endemic species of Gelidium have been described from the remote Tristan da Cunha archipelago. A recent barcode survey of Tristan da Cunha red algae in combination with the clarification of vouchers for previously sequenced specimens has prompted a molecular and morphological reassessment of these species. Analyses of rbc L and COI-5P data indicated that all sequenced Tristan da Cunha specimens represented a single taxon, and furthermore that this genetic group was conspecific with Gelidium micropterum from southern Africa. Morphologically the Tristan da Cunha specimens represented either Gelidium concinnum or Gelidium regulare , and there was a grade of character states between both of these species, as well as G. micropterum . Based on these results the synonymy of G. concinnum and G. regulare under G. micropterum is proposed and an expanded description of G. micropterum provided. None of the studied Tristan da Cunha specimens clearly fit the description of the third endemic species, Gelidium inflexum , and its status could not be determined.

Sargassum species form large beds that play an important role in coastal ecosystems. The beds are abundant and Sargassum is often used as food and in Asian medicine in Vietnam. As a base for future use and conservation, we surveyed 14 species of Sargassum at eight locations during April-May of 2018 and 2019. Sargassum species from Vietnam were divisible into northern and southern groups; the northern group comprised Sargassum graminifolium , Sargassum herklotsii , and Sargassum cotoense , which occur in the North and North Central zones. The southern group comprised Sargassum bicorne , Sargassum feldmannii , Sargassum ilicifolium , Sargassum swartzii , and two endemic species, Sargassum phamhoangii and Sargassum quinhonense , which occur in the Central to South West zones. Three species, Sargassum aquifolium , Sargassum oligocystum , and Sargassum polycystum , were widespread along the long coast of Vietnam. This is the first report on distribution patterns of Sargassum species along the long coast of Vietnam. Our study provides baseline data for evaluating ecological disturbance and risks of Sargassum -associated ecosystems.

A survey of driftwood and mangrove wood in South Australia revealed a high diversity of marine fungi. Across eight sites there were 43 species of marine fungi, of which 42 are new records for South Australia, 11 new records for Australia and 12 taxa currently of uncertain status likely to be new species. Sites had distinctive species compositions with the largest difference attributable to substrate type (beach driftwood vs. mangrove wood). However, even between mangrove sites, species assemblages were distinctly different with only the more common species occurring at all mangrove sites. More intensive surveys across a broader range of habitats and geographic locations should reveal significantly more species.

Agarophyton vermiculophyllum is a commercially important red alga for agar production in the Northwest Pacific Ocean and is an invasive seaweed in Europe. High temperature is an important environmental stressor that influences its growth, metabolism, and migration. Nevertheless, little is known about the molecular mechanisms underpinning the response of A. vermiculophyllum to heat stress. Using RNA-sequencing, we performed the first comprehensive transcriptome analysis of A. vermiculophyllum under heat stress to explore and identify potentially important heat stress-responsive genes. After de novo assembly of the transcriptome, 55,486 unigenes were found, of which 39,687 unigenes (71.52%) were functionally annotated. In total, 2,923 differentially expressed genes (DEGs) were detected between heat-stressed and control samples. Heat shock proteins represented the most abundant DEGs. Transcript factors were also significantly differently expressed under heat stress. Meanwhile, the photoprotective mechanism based on PsbS (Photosystem II subunit S) related nonphotochemical quenching and PGR5 (proton gradient regulation 5) dependent cyclic electron flow around photosystem I was found to be promoted under heat stress, which may help A. vermiculophyllum to cope with the high temperature. This study lays an important foundation for further elucidation of the molecular mechanism underlying heat tolerance in A. vermiculophyllum .