Global trends in the occurrence, toxicity and risk posed by harmful algal blooms to natural systems, human health and coastal economies are poorly constrained, but are widely thought to be increasing due to climate change and nutrient pollution. Here, we conduct a statistical analysis on a global dataset extracted from the Harmful Algae Event Database and Ocean Biodiversity Information System for the period 1985–2018 to investigate temporal trends in the frequency and distribution of marine harmful algal blooms. We find no uniform global trend in the number of harmful algal events and their distribution over time, once data were adjusted for regional variations in monitoring effort. Varying and contrasting regional trends were driven by differences in bloom species, type and emergent impacts. Our findings suggest that intensified monitoring efforts associated with increased aquaculture production are responsible for the perceived increase in harmful algae events and that there is no empirical support for broad statements regarding increasing global trends. Instead, trends need to be considered regionally and at the species level.

Taxonomic data on phytoplankton composition is important for ecological studies, however, such information is not easy to gather. Imaging devices and image classification software have been developed in the past decades for rapid phytoplankton assessment. Taxonomic resolution output of classification software are primarily limited by the quality of images produced by these imaging instruments. FlowCAM has been utilized in several studies for this endeavor. However, the phytoplankton categories that the instrument is currently able to discriminate are still few compared to the outputs of microscopy. This study aimed to produce high resolution FlowCAM images of fixed phytoplankton samples from natural environments without compromising sample analysis time. It was also aimed to optimize the capability of FlowCAM's VisualSpreadsheet software to automatically classify phytoplankton images. The use of FOV300 flow cell and 10X objective combination has proven to be effective in producing good quality images at a faster rate. The modified hardware configuration resulted to FlowCAM counts that were comparable to that of the standard microscopy method. FlowCAM was able to automatically classify images of dominant phytoplankton groups in the two key sardine fishery areas in the Philippines with relatively high accuracy values. These phytoplankton groups are represented by genera with complex morphological structures (e.g., setae) such as Chaetoceros and Bacteriastrum as well as those genera with simple shapes such as Pseudo‐nitzschia (thin‐elongate) and Coscinodiscus (spherical).

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The lateral variation of sediment properties and associated cyst content of sediment in Manila Bay were determined and their possible role/s in the occurrences of Pyrodinium bahamense Plate var. compressum (Böhm) Steidinger, Tester et Taylor toxic blooms were assessed. Manila Bay's surface sediment was determined to be silt dominated. Clay generally increased towards the coast, probably as a result of flocculation and rapid deposition upon entry of sediments from the rivers. High sand content characterized the southeastern part of the bay attributed to the greater sand inputs and relatively strong currents in this area. Bulk densities were lower in the eastern side of the bay from dilution by high organic load from sewage and urban areas. Benthic flux calculations, particularly NH3, suggest more than 50% nutrient contribution comes from sediments.In general, dinoflagellate cyst density increased from the center of the bay towards the coast, except in Pampanga Bay where it decreased near the coasts. A maximum of 23 dinoflagellate species were identified: 5 were autotrophic ( Lingulodinium polyedrum (Stein) Dodge , Gonyaulax spp., Pyrophacus steinii (Schiller) Wall et Dale , Protoceratium reticulatum (Claparéde et Lachmann) Bütschli , and Pyrodinium bahamense var. compressum ), and the rest were predominantly composed of Protoperidinium spp. and Diplopsalis spp. Heterotrophs comprised about 70% of the total cyst counts. Pyrodinium counts increased towards the north-western part of the bay where it was the dominant autotroph species. Negative correlations were observed for live Pyrodinium cyst density and N flux, P flux, ratio of N to P and total organic carbon (TOC) content. However, areas with high N:P ratio contain abundant Pyrodinium live cysts.

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Coral reefs of the North Indo-West Pacific provide important ecosystem services to the region but are subjected to multiple local and global threats. Strengthening management measures necessitate understanding the variability of larval connectivity and bridging global connectivity models to local scales. An individual-based Lagrangian biophysical model was used to simulate connectivity between coral reefs for three organisms with different early life history characteristics: a coral ( Acropora millepora ), a sea urchin ( Tripneustes gratilla ), and a reef fish ( Epinephelus sp). Connectivity metrics and reef clusters were computed from the settlement probability matrices. Fitted power law functions derived from the dispersal kernels provided relative probabilities of connection given only the distance between reefs, and demonstrated that 95% of the larvae across organisms settled within a third of their maximum settlement distances. The magnitude of the connectivity metric values of reef cells were sensitive to differences both in the type of organism and temporal variability. Seasonal variability of connections was more dominant than interannual variability. However, despite these differences, the moderate to high correlation of metrics between organisms and seasonal matrices suggest that the spatial patterns are relatively similar between reefs. A cluster analysis based on the Bray-Curtis Dissimilarity of sink and source connections synthesized the inherent variability of these multiple large connectivity matrices. Through this, similarities in regional connectivity patterns were determined at various cluster sizes depending on the scale of interest. The validity of the model is supported by 1) the simulated dispersal kernels being within the range of reported parentage analysis estimates; and, 2) the clusters that emerged reflect the dispersal barriers implied by previously published population genetics studies. The tools presented here (dispersal kernels, temporal variability maps and reef clustering) can be used to include regional patterns of connectivity into the spatial management of coral reefs.

Microbes are central to the structuring and functioning of marine ecosystems. Given the remarkable diversity of the ocean microbiome, uncovering marine microbial taxa remains a fundamental challenge in microbial ecology. However, there has been little effort, thus far, to describe the diversity of marine microorganisms in the region of high marine biodiversity around the Philippines. Here, we present data on the taxonomic diversity of bacteria and archaea in Benham Rise, Philippines, Western Pacific Ocean, using 16S V4 rRNA gene sequencing. The major bacterial and archaeal phyla identified in the Benham Rise are Proteobacteria, Cyanobacteria, Actinobacteria, Bacteroidetes, Marinimicrobia, Thaumarchaeota and, Euryarchaeota. The upper mesopelagic layer exhibited greater microbial diversity and richness compared to surface waters. Vertical zonation of the microbial community is evident and may be attributed to physical stratification of the water column acting as a dispersal barrier. Canonical Correspondence Analysis (CCA) recapitulated previously known associations of taxa and physicochemical parameters in the environment, such as the association of oligotrophic clades with low nutrient surface water and deep water clades that have the capacity to oxidize ammonia or nitrite at the upper mesopelagic layer. These findings provide foundational information on the diversity of marine microbes in Philippine waters. Further studies are warranted to gain a more comprehensive picture of microbial diversity within the region.

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