Tropical Coastal Environments Research Articles

Progress in Research on Microplastic Prevalence in Tropical Coastal Environments: A Case Study of the Johor and Singapore Straits

Microplastics are contaminants in marine ecosystems, posing great threats to biota and human health. In this work, we provide an overview of the progress made in understanding microplastic prevalence in tropical coastal environments, focusing on the Johor and the Singapore Straits as a case study. We examine the sources, distribution, transport, and ecological impact of microplastic pollution in this region through a systematic review. All papers relating to marine microplastics in Singapore’s sand and benthic sediments, seawater, and marine biota were used for analysis, from 2004 to 2023. In addition, we discuss the influence of envi-ronmental factors such as coastal morphology and anthropogenic activities on patterns of microplastic accumulation. We emphasize that microplastic pollution is more prevalent along the eutrophic Johor Strait compared to the Singapore Strait due to hydrological conditions. Rainfall is also a key factor that influences mi-croplastic abundance during the monsoon seasons. Furthermore, the bacterial and plankton assemblages of organisms on microplastic surfaces are diverse, with eutrophic waters enhancing the diversity of organisms on microplastic surfaces. Novel harmful cyanobacteria and bloom species of phytoplankton were also found on microplastic surfaces. By synthesizing existing research findings and highlighting regional characteristics, this paper contributes to ongoing efforts to mitigate microplastic pollution in tropical regions.

Progress in Research on Microplastic Prevalence in Tropical Coastal Environments: A Case Study of the Johor and Singapore Straits

Microplastics are contaminants in marine ecosystems, posing great threats to biota and human health. In this work, we provide an overview of the progress made in understanding microplastic prevalence in tropical coastal environments, focusing on the Johor and the Singapore Straits as a case study. We examine the sources, distribution, transport, and ecological impact of microplastic pollution in this region through a systematic review. All papers relating to marine microplastics in Singapore’s sand and benthic sediments, seawater, and marine biota were used for analysis, from 2004 to 2023. In addition, we discuss the influence of envi-ronmental factors such as coastal morphology and anthropogenic activities on patterns of microplastic accumulation. We emphasize that microplastic pollution is more prevalent along the eutrophic Johor Strait compared to the Singapore Strait due to hydrological conditions. Rainfall is also a key factor that influences mi-croplastic abundance during the monsoon seasons. Furthermore, the bacterial and plankton assemblages of organisms on microplastic surfaces are diverse, with eutrophic waters enhancing the diversity of organisms on microplastic surfaces. Novel harmful cyanobacteria and bloom species of phytoplankton were also found on microplastic surfaces. By synthesizing existing research findings and highlighting regional characteristics, this paper contributes to ongoing efforts to mitigate microplastic pollution in tropical regions.

Seagrass mapping across the coast of Tanzania

Seagrasses are marine flowering plants found in both temperate and tropical coastal environments, that offer vital ecosystem services and adaptations. However, due to their proximity to the shore, they are heavily impacted by human activities and climate change, endangering seagrasses and their services. To manage seagrass meadows effectively and sustainably, detailed monitoring and data on distribution and extent are essential. Unfortunately, past under-prioritization of reliable baseline data impedes understanding of ecosystem dynamics and rapid response to declines. This study employs satellite imagery, coupled with ground truthing, to comprehensively report seagrass coverage along Tanzania's mainland coast and Zanzibar islands. By utilizing machine-learning technologies, the study achieves 84.2% accuracy, and found that Tanzania has 2817 km2 of seagrass coverage, which is five times higher than previously reported. In addition, the results also provide coverage of additional benthic habitats, such as corals, rocks/rubble, and sand. This study provides the first comprehensive overview of seagrass coverage in Tanzania and will function as a valuable tool and baseline for understanding and managing these habitats. The findings suggest that seagrasses in Tanzania are still relatively abundant, but due to a number of threats, including pollution, coastal development, and climate change, these habitats require improvement in management strategies including regular monitoring to understand their status and trends in their area coverage. The study highlights the significance of remote sensing and machine learning in mapping and monitoring coastal habitats across extensive geographical areas. We aspire for the presented results to be utilized among stakeholders and researchers to develop more effective conservation measures for seagrasses in Tanzania and the Western Indian Ocean.

Plankton assemblages from microplastics of tropical coastal environments reveal high diversity and evidence of toxic species

Microplastics are a major constituent of plastic waste and are of an increasing global concern. Although microplastics are prevalent in marine ecosystems, the characterisation of plankton communities has been largely neglected in this aspect, especially in tropical ecosystems. To better understand the role of microplastics as a carrier of harmful plankton in marine ecosystems, epiplastic plankton communities in tropical marine ecosystems were studied from beach sediments along the Johor and Singapore Straits. Complementary analysis of microscopy and high throughput sequencing of the 16S rRNA (V3–V4) and 18S (V4) rRNA regions provided evidence that the plastisphere provided an appropriate environment to host a wide range of planktonic organisms. An average of 781 OTUs were identified across the three sampling sites. The structures of plankton communities were distinct across the sampling sites and were generally dominated by dinoflagellates, fungi and chlorophytes. We demonstrate that marine microplastics serve as microhabitats that are a host to harmful phytoplankton species, including viable resting cysts of dinoflagellates. Furthermore, plastics isolated from the location with the greatest anthropogenic influence demonstrated the greatest plankton diversity. This study presents evidence of diverse toxic plankton species present on the plastisphere and highlights its importance as a vector of the transport of harmful opportunistic species in relation to anthropogenic influence, in the marine environment.

Sediment-driven plastisphere community assembly on plastic debris in tropical coastal and marine environments

Coastal habitats have been suggested to serve as a sink for unaccounted plastic debris, i.e., “missing plastic” in the sea, and hence, a hotspot of plastic pollution in the marine and coastal environments. Although the accumulation of plastic debris may pose significant threats to coastal ecosystems, we know little about the fate of these plastic debris and their ecological impacts due to the lack of studies on plastic-microbe interactions in coastal habitats, especially for the tropical marine and coastal environments. In this study, we collected plastic debris from 14 sites consisting of various coastal ecosystems (seagrass meadows, mangrove forests, and beaches), and marine ecosystem (coral reef) around Singapore and characterized the prokaryotic and eukaryotic microbial communities colonized on them. Our results showed that the composition of plastisphere communities in these intertidal ecosystems was predominantly influenced by the sediment than by the plastic materials. Compared with surrounding sediment and seawater, the plastic debris enriched potential plastic degraders, such as Muricauda, Halomonas, and Brevundimonas. The plastic debris was also found to host taxa that play significant roles in biogeochemical cycles (e.g., cyanobacteria, Erythrobacter), hygienically relevant bacteria (e.g., Chryseobacterium, Brevundimonas), and potential pathogens that may negatively impact the health of coastal ecosystems (e.g., Thraustochytriaceae, Labyrinthulaceae, Flavobacterium). Taken together, our study provides valuable insights into the plastic-microbe interactions in tropical coastal and marine ecosystems, highlighting the urgent need for plastisphere studies to understand the fate and ecological impacts of plastic debris accumulated in coastal habitats.

Assessment of Infiltration Swale Performance as a Low-Impact Development Technique in Tropical Coastal Environments

Operation of source control measures (SCM) in urban drainage in tropical/transitional climates are still a challenge because of higher rain volumes and more intense rains, as well as constraints from sea-level interference. In this study, the performance of a swale to control runoff was detailed and monitored in such an environment. The data on rain, runoff, and sea levels were acquired at a site located in an island in the south coast of Brazil. The results showed that even with higher rain volumes and more intense rains, the mean capture of the swale was 51.7% of the entrance runoff volume, but it depended on seasonal rain variation and interference of sea/tide level. As a result, the swale might be undersized in summer and oversized in winter. Peak flow retardation was observed in 97% of monitored events. The interference of sea/tide level was not directly correlated with infiltration volumes, but in the principal component analysis, the parameters of sea/tide level, along with the hydrological parameters of rain duration, height, and intensity, explained 60% of the variance in the data. In conclusion, the application of SCMs in tropical regions is suitable, but seasonality should be incorporated in the design. The interference of sea/tide level must be further investigated to verify how to incorporate its influence in the design.

Grounding the SHIELD Model for Tropical Coastal Environments

Customizing environmental assessments to the particularities of the type of environment is crucial for implementing the precautionary principle. This paper uses the SHIELD model (Susceptibility to Human Interventions for Environmental Licensing Determination) in the context of geomorphology for the effective management of coastal environments. This paper describes the customization of the SHIELD model for tropical coastal environments as a way of validating a specific kind of environment. The assessment translates expert knowledge into technical criteria for the environmental control of human interventions through fuzzy logic computations. This assessment identified 21 geomorphological processes across six categories. Moreover, computation of the parameters resulted in a database of susceptibility measures for 4524 interactions. These quantitative results could guide future environmental impact studies of coastal environments, considering licensing instrument requirements. The SHIELD model approach, illustrated here on tropical coastal environments, offers a technical alternative for improving the environmental control of anthropogenic impacts from a geomorphological perspective.

Lost in the wind: An integrated approach for the recognition of mixed clastic–carbonate continental aeolianites

AbstractAeolianites with a mixed clastic and carbonate detrital mineralogy are typical deposits of tropical coastal desert environments. These deposits are genetically related to transgressive–regressive cycles, with the shallow‐marine carbonate detrital component being deflated from the exposed seafloor during episodes of glacial sea‐level lowstands, transported and later accumulated onto more continental areas. A detailed investigation of the granulometric and petrographic properties of the Late Pleistocene to Holocene Ghayathi Formation in the United Arab Emirates provides a comprehensive numerical dataset that reveals the complex spatio‐temporal depositional and diagenetic evolution of a mixed siliciclastic–carbonate continental aeolianite. Fifty‐one thin sections and forty‐four rock samples of three sedimentary units (Madinat‐Zayed, Ghayathi and Fuwayrit formations) from the United Arab Emirates were analyzed for their grain‐size distribution, mineralogy and the bulk stable‐carbon and oxygen isotopic composition. Sorting, skewness and kurtosis of the grain‐size distributions provide evidence for a divergent aerodynamic behaviour between the carbonate and siliciclastic particles. The different grain‐size distributions between the inland and coastal sections of the Ghayathi Formation indicate that continental mixed clastic−carbonate aeolianites are affected by density‐driven selective transport and consequent traction sorting due to the nature of carbonate detritus. The transport decoupling of the different detrital components resulted in a ‘continental sorting’ effect, with the inland sections yielding layers characterized by a better sorted detritus than the coastal areas. All detritus originally composed of aragonite has been removed by dissolution during early meteoric diagenesis, with its shapes frequently preserved by micritic envelopes. The bulk stable‐isotope composition of the carbonate fraction reflects a decreasing degree of meteoric cementation from coastal to inland areas. The high complexity of the lateral and vertical distribution of the sedimentary, diagenetic and isotopic properties of continental mixed aeolianites, such as the Ghayathi Formation, highlights the problem of recognizing such deposits in the pre‐Quaternary sedimentary record.

The irrelevance of scale and fixedness in landscape terms in two Australian languages

AbstractThis article examines how the speakers of Manyjilyjarra (Great Sandy Desert) and Umpila/Kuuku Ya’u (Cape York Peninsula) linguistically categorize the landscape in which they live. Located on opposite sides of Australia, in highly contrasting arid inland and tropical coastal environments, the semantics of the landscape feature terminology in these two Australian languages have key similarities. Both lexical sets overwhelmingly classify the landscape with the use of abstract and general concepts of shape and material make-up. Together with a lack of specification of size or fixedness in this terminology, this presents intriguing issues for received conceptualizations of landscape in the geosciences and language sciences. This article finds that complex and recurrent interests in material make-up extend beyond landscape feature terminology in both languages and reveal possible cultural priorities underlying the semantic patterns.

Seasonal variations in the backscatter of RADARSAT-1 images in tropical coastal environments

Seasonal variations in the backscatter of RADARSAT-1 images in tropical coastal environments

The neritid snails of Brunei Darussalam: their geographical, ecological and conservation significance

Neritid snails are diverse and conspicuous in tropical coastal environments. They can serve as indicators of environmental change and can provide conservation information. In the present review of the neritid species of Brunei Darussalam, we report sixteen species, including seven new records from estuarine, mangrove and rocky-shore habitats. These records update distributions across the Central Indo-Pacific realm, specifically the Palawan/North Borneo ecoregion. Under-sampling, species misidentifications and locally-rare species undermine the accuracy of records in previous studies for the region. Three of the rocky-shore and two of the mangrove species collected here are represented by single specimens; these rocky-shore species are possible colonizers from neighbouring regions and the scarcity of the mangrove species likely refers to under-sampling. We present novel shell characteristics that readily distinguish between Neripteron violaceum and Nerip. cornucopia. We describe the ecology and habitat use of the Brunei species and discuss conservation issues.

Using mud crabs (Scylla serrata) as environmental indicators in a harbour health report card

ABSTRACT Report cards are increasingly popular tools communicating the condition of coastal and riverine environments to environmental managers, stakeholders and the public, and synthesising complex data drawn from a range of indicators. Mud crabs have not previously been included in ecosystem health report cards in Australia or elsewhere but have been suggested as environmental indicators for tropical coastal marine environments in Australia. Mud crabs support commercial, recreational and Indigenous fisheries and their biology is relatively well known. For these reasons and due to their local relevance, mud crabs (Scylla serrata) were selected for long-term monitoring and inclusion in a report card for Gladstone Harbour, Australia. Three mud crab measures were identified to reflect the variety of pressures across Gladstone Harbour: abundance, prevalence of rust lesions and sex ratio. A standardised field monitoring program was developed to allow for ongoing scoring and reporting of the multi-metric indicator. An indicator scoring (distance from benchmark) and grading methodology was applied to the indicator and refined over the two years of monitoring. This article provides a novel framework for monitoring and scoring mud crabs for management purposes or for use in report cards, and outlines the process of developing an indicator for an iconic crustacean species.

Hydro-Geochemical Mechanisms of Brackish Shallow Groundwater Development- Coastal Greater Accra Region, Ghana

This study investigated the processes influencing the chemistry of surface and shallow groundwater in tropical coastal environments - south east of greater Accra region of Ghana using GIS models and combination of geological and hydro geochemical techniques for sustainable management of freshwater resources and abundantly available brackish water resources. A total of 37 shallow groundwater and 11 surface water samples were collected and analysed for their physico-chemical constituents.
 The samples were adjusted to room temperature after which the hydrogen ion concentration (pH), Total Dissolve Solids (TDS) and Electrical Conductivity were measured with a precision of 0.01 for both parameters using a La Motte, USA in unfiltered samples. The analysis of major and minor ions were performed using ion chromatography (DIONEX-ICS-1000 Series). The geographical locations of the samples were recorded with the aid of a handheld Global Position System (GPS).
 The analysed shallow groundwater indicates minimum salinity values of 70.2 psu/ppm, maximum salinity of 4398.3 psu/ppm with an average of 1571.4 psu/ppm whilst surface water has minimum salinity of 33.8 psu/ppm, maximum of 43574 psu/ppm with an average of 4972.6 psu/ppm therefore highly saline. The total minimum dissolved solid (TDS) concentrations is 87.5 ppm, maximum of 5160 ppm with an average of 1911.96 ppm for shallow groundwater and for surface water minimum of 38.4 ppm, maximum of 27100 ppm and average 3938.12 ppm.

Metal resistance genes enrichment in marine biofilm communities selected by biocide-containing surfaces in temperate and tropical coastal environments.

Microorganisms able to form biofilms in marine ecosystems are selected depending on immersed surfaces and environmental conditions. Cell attachment directly on toxic surfaces like antifouling coatings suggests a selection of tolerant (or resistant) organisms with characteristics conferring adaptive advantages. We investigated if environment would drive metal resistance gene abundance in biofilms on artificial surfaces. Biofilms were sampled from three surfaces (a PVC reference and two antifouling coatings) deployed in three coastal waters with dissimilar characteristics: The Mediterranean Sea (Toulon) and Atlantic (Lorient) and Indian (Reunion) Oceans. The two coatings differed in metals composition, either Cu thiocyanate and Zn pyrithione (A3) or Cu2O (Hy). Metal resistance genes (MRG) specific to copper (cusA, copA, cueO) or other metals (czcA and pbrT) were monitored with qPCR in parallel to the microbial community using 16S rRNA gene metabarcoding. A lower α-diversity on A3 or Hy than on PVC was observed independent on the site. Weighted Unifrac suggested segregation of communities primarily by surface, with lower site effect. Metacoder log2 fold change ratio and LeFSe discrimination suggested Marinobacter to be specific of Hy and Altererythrobacter, Erythrobacter and Sphingorhabdus of A3. Likewise, the relative abundance of MRG (MRG/bacterial 16S rRNA) varied between surfaces and sites. A3 presented the greatest relative abundances for cusA, cueO and czcA. The latter could only be amplified from A3 communities, except at Toulon. Hy surface presented the highest relative abundance for copA, specifically at Lorient. These relative abundances were correlated with LeFSe discriminant taxa. Dasania correlated positively with all MRG except cueO. Marinobacter found in greater abundance in Hy biofilm communities correlated with the highest abundances of copA and Roseovarius with czcA. These results prove the selection of specific communities with abilities to tolerate metallic biocides forming biofilms over antifouling surfaces, and the secondary but significant influence of local environmental factors.

Marine soundscape and fish chorus in an archipelago ecosystem comprising bio-diverse tropical islands off Goa Coast, India

Many biological sources of sound in tropical coastal shallow-water marine environments remain unidentified. Characterizing the soundscape of such environments requires that all sources of biological sound be examined for their distinct patterns and specific frequency ranges. The present study identified soniferous fish in the ecosystem and measured underwater ambient sound in terms of its sound pressure levels (SPL) to quantify and characterize their contribution to the soundscape. Underwater SPLs were measured from 2012 to 2016 at a site near Grande Island Archipelago (15° 18′ N, 73° 41′ E) 18 km off the coast of the state of Goa, which lies along India’s western coast. Acoustic data were recorded using three types of methods for passive acoustic monitoring, namely a hanging hydrophone, five seabed-mounted hydrophones and an autonomous moored vertical hydrophone. Underwater visual census at the site revealed that both species richness and diversity were high indicating the Grande Island Archipelago is a bio-diverse site. The seabed-mounted hydrophones proved to be the best choice for long-term SPL measurements, although the moored arrays were more economical. Ambient sound levels underwater varied markedly over time both within a day and with the season. Long-term SPLs were above 100 dB re 1 μPa over frequencies 62.5–8000 Hz and peaked to 120–130 dB re 1 μPa between frequencies 500 Hz and 1000 Hz, corresponding to the chorus frequencies of soniferous fish at the site. High SPLs and marked temporal variations of the soundscape indicate the abundance, diversity and life activities of fish species and healthy ecological state of the bio-diverse archipelago.

Effect of Alternate Wetting and Drying on some Properties of High Strength Concrete in Tropical Coastal Environments

Concrete is one of the most used construction materials in the world, due to its good durability and fire resistance properties, versatility in forming various shapes, abundance of raw materials and low manufacturing and maintenance costs. High strength concrete, which is a type of concrete, finds its application in construction of high rise buildings, bridges, highways, etc. Its physical properties are greatly affected by the method of curing and the environment in which it is placed. This study investigated the effect on the compressive strength and some transport properties of high strength concrete subjected to alternate wetting and drying exposure, which may be due to intermittent rains, or rise and fall in tides of the sea, an exposure type that is commonly experienced in coastal areas. High strength concrete samples were prepared and subjected to two different curing regimes, one in which the concrete samples were cured continuously under water, and the other in which the concrete samples were subjected to 12-hr curing under water followed by 12-hr curing under ambient air. Various tests such as ultrasonic pulse velocity (UPV), compressive strength, water and chloride ingress tests were conducted on the cured concrete samples. The results obtained from the tests conducted, generally showed that the strength and transport properties of the high strength concrete was greatly affected by the alternate wetting and drying curing method. The effect was seen to be more adverse at the later ages than at the early ages.

Provenance of Eocene–Oligocene sediments in the San Jacinto Fold Belt: Paleogeographic and geodynamic implications for the northern Andes and the southern Caribbean

AbstractMesozoic and Cenozoic strata of the San Jacinto Fold Belt (Colombian Caribbean) provide insights about sedimentary environments and paleogeographic evolution in the transition between the northern Andes and the South Caribbean deformed belt. We report new provenance (conventional sandstone petrography, heavy mineral analysis, and detrital zircon U-Pb geochronology and typology) and micropaleontologic data (palynology, calcareous nannofossils, and foraminifera) in samples collected from the lower Eocene (San Cayetano Formation) and upper Eocene–Oligocene (Toluviejo and Ciénaga de Oro Formations) rocks in boreholes drilled by the Colombian Agencia Nacional de Hidrocarburos as well as from recently exposed Oligocene outcrops from the Ciénaga de Oro Formation. Sandstone petrography shows modal variations, with high feldspar content in the lower Eocene rocks and high quartz content in the Oligocene deposits. This shift in compositional maturity may be due to climatic variations, tectonic activity, and/or changes in source areas. Heavy mineral analyses indicate variations that suggest sources primarily related to felsic igneous and/or low-grade metamorphic and mafic and ultramafic rocks. Zircon U-Pb geochronology displays age populations mainly in the Late Cretaceous, Late Jurassic, Permian–Triassic, and Precambrian (ca. 900–1500 Ma). In addition, zircon typology analyses indicate that the igneous zircons came primarily from monzogranites and granodiorites. Finally, the micropaleontologic and sedimentary data sets indicate that the sediments were deposited in tropical coastal and shallow marine environments. The sediments were transported by short rivers from the crystalline massifs of the Lower Magdalena Valley and the northern Central Cordillera basements, while distal transport of sediments may have occurred along longer rivers, which brought sediments from southern regions located between the Central and Western Cordilleras.

Inventory of aliphatic hydrocarbons in a tropical mangrove estuary: a biomarker approach

Aliphatic hydrocarbons in the sediments of the estuarine mangrove forests of Cochin region, Southwest coast of India were characterized to assess the sources of organic matter (OM) and to validate the effectiveness of the various geochemical indices to identify multiple OM sources and the complex geochemistry of these tropical coastal environments. The total concentration of the n-alkanes varied from 606.39 to 826.25 µg/g [dry weight (dw)] in mangrove sediments, to values between 230.10 and 287.67 µg/g in estuarine sediments. The n-alkane distribution in the study region indicated a strong odd over even predominance in both mangrove and estuarine sediments. Assessment using terrestrial OM indices such as Carbon Preference Index (CPI), Terrigenous Aquatic Ratio (TAR), and Terrestrial Marine Discriminant (TMD) suggested that a large fraction of OM in the mangrove sediments was derived from mangrove plant litter and a better preservation of mangrove OM in the sedimentary environment has occurred. These findings are supported by the higher content of total lipid, tannin, and lignin, as well as by the depleted δ13C values. Low ratios of CPI, TAR, and TMD at estuarine sites E2 and E3 indicated a mixed origin of OM. Natural or biogenic indices such as natural n-alkanes ratio (NAR), Σn-alkanes/n-C16, n-C29/n-C17, and LMW/HMW revealed that all the mangrove stations and the estuarine station E1 received OM from natural or biogenic sources, whereas a significant anthropogenic input was noticed for estuarine stations E2 and E3. Indices like Pr/Ph, Pr/n-C17, Ph/n-C18 further confirmed the mixed nature of OM accumulated under the anoxic environment.

Sources of organic matter in two contrasting tropical coastal environments: The Caribbean Sea and the eastern Pacific

In this study, we evaluate sources of organic matter (OM) in two contrasting tropical coastal environments in Colombia, using a combination of glycerol dialkyl glycerol tetraethers (GDGTs) and n-alkane lipid biomarkers. A clear difference between the less productive Caribbean Sea and the more productive eastern Pacific is observed, with higher terrestrial contributions into the eastern Pacific strongly associated with riverine inputs. Although higher land plant-derived n-alkanes can be transported as eolian dust, our results suggest mainly riverine sources for our samples. When looking at the branched GDGT compositions, in situ production could be identified in most Caribbean stations and some of the more coastal sites in the Pacific with #ringstetra index values of above 0.7. The remaining stations in the eastern Pacific display soil-eroded GDGTs inputs associated with river discharges and deposited in the proximity of the coast. Marine production as measured by short chain n-alkanes and crenarchaeol are also higher in the eastern Pacific. It appears that the terrestrial inputs would bring nutrients as well as OM fueling both auto- and heterotrophs making the eastern Pacific overall more productive. We also observe OM of petrogenic origin, albeit in a low amount, especially in coastal Caribbean sites located near main harbors. This study helps improve the understanding of the complex mixture of OM inputs, origins and transport mechanisms into Colombian coastal areas. The present work emphasizes the need to integrate climate, geological setting and hydrology to fully understand the carbon cycle at a regional scale.

Biodiversity of benthic filamentous cyanobacteria in tropical marine environments of Bahia State, Northeastern Brazil

This study aimed to better understand the biodiversity and ecological aspects of benthic filamentous cyanobacteria along the coast of an extensive Brazilian tropical region with underestimated biodiversity. We collected samples between 2010 and 2012 in 24 areas along the coast of the State of Bahia, Northeastern Brazil. We analyzed biodiversity, life form, and spatial distribution of filamentous cyanobacteria on various marine substrata. The intertidal area was divided into three microhabitats according to hydrodynamics: tidal pools, protected reef region, and front reef region. Thirty-two taxa were identified and Oscillatoriales showed the highest biodiversity (16 taxa), followed by Nostocales (9), Synechoccocales (5) and Spirulinales (2). We reported 22 new references to Bahia State. Twenty-two taxa occurred only in one beach, and Symploca cf. hydnoides Gomont was the only widely distributed along the coast of Bahia. Epilithic (21 taxa) and epiphytic (15) showed the greatest species richness. Only two species presented epizoic life form. We observed the highest species richness in the protected reef region (17 taxa). We found eleven and eight taxa in the tidal pool and supralittoral zone, respectively. No cyanobacteria were found in the front reef region, an area with high hydrodynamics. This research presented many taxa in common with previous studies on cyanobacterial diversity developed in other tropical regions around the globe. The great biodiversity and new records reported in this study highlight the need of further surveys in tropical coastal environments, areas still underexplored in terms of biodiversity of cyanobacteria.