Epibiotic bacteria on the carapace of hawksbill and green sea turtles.

In this study, epibiotic bacteria on the carapace of sea turtles at three different sites in the Persian Gulf were studied. Bacterial density counted using a Scanning Electron Microscope showed that the highest (9.4 × 106 ± 0.8 × 106 cm-2) and lowest (5.3 × 106 ± 0.4 × 106 cm-2) average bacterial densities were found on the green and hawksbill sea turtles, respectively. Bacterial community analysis using Illumina 16S rRNA gene sequencing showed that Gamma- and Alpha-proteobacteria were the dominant classes on all substrates. Some genera, such as Anaerolinea, were site- and substrate-specific. In general, bacterial communities on sea turtles differed from those on the non-living substrate, stones, and exhibited lower species richness and diversity compared to the latter. Despite some similarities, the majority of bacterial communities on the two sea turtles were different. This study provides baseline information about the epibiotic bacteria of sea turtles of different species.

Temporal variations of biofouling assemblages of a coral reef ecosystem during a monsoon period.

Coral reefs are highly biodiverse ecosystems, enriched by a range of biofouling species. Temporal variations in biofouling can affect ecosystem stability, but these diverse coral-associated communities remain underexplored in some regions. In the present study, biofouling assemblages of coral reefs in the Chabahar Bay were investigated during a summer monsoon at three deployment periods. In total, 26 taxa were identified with barnacles and polychaetes being the dominant taxa during the whole study. The coverage percentage was driven mostly by the encrusting taxa such as bryozoans and algae while biomass was determined by the dominance of shell-forming taxa. The results of PERMANOVA showed that the effects of the submersion period were significant on the assemblage structure. Biofouling assessment plays a pivotal role in safeguarding the intricate balance and long-term health of coral reef ecosystems. For a comprehensive understanding of biofouling dynamics and interactions with coral-associated species, conducting long-term studies is vital.

Impact of warming on biofouling communities in the northern Persian Gulf.

While the impact of ocean warming on single species is well described, the impact on marine biofouling communities is not well understood. Effluents of power plants have higher temperatures and can be used as natural large-scale test sites to investigate warming effects on marine ecosystems. In the present study, we evaluated the impact of elevated temperatures in the vicinity of a power plant on macro-biofouling communities in the northern coast of the Persian Gulf. The impact site was on average 2 °C warmer than the control site. Our results demonstrate a significantly different structure and composition of biofouling communities between control and impact sites. Warming led to a 1.5-fold increase in the mean coverage of biofouling communities and slightly decreased functional and species richness. Our results indicated that future warming will likely increase biofouling pressure, while decreasing diversity of communities, particularly in habitats where organisms exist at their upper tolerance limits of temperature.

Assemblage of encrusting organisms on floating anthropogenic debris along the northern coast of the Persian Gulf.

Global concern about floating marine debris and its fundamental role in shaping coastal biodiversity is growing, yet there is very little knowledge about debris-associated rafting communities in many areas of the world's oceans. In the present study, we examined the encrusting assemblage on different types of stranded debris (wood, plastic, glass, and metal cans) along the Iranian coast of the Persian Gulf. In total, 21 taxa were identified on 132 items. The average frequency of occurrence (±SE) across all sites and stranded debris showed that the barnacle Amphibalanus amphitrite (68.9 ±â€¯1.1%), the oyster Saccostrea cucullata (40.9 ±â€¯0.7%), the polychaete Spirobranchus kraussii (27.3 ±â€¯0.5%), green algae (22 ±â€¯0.5%) and the coral Paracyathus stokesii (14.4 ±â€¯0.7%) occurred most frequently. Relative substratum coverage was highest for A. amphitrite (44.3 ±â€¯2.7%), followed by green algae (14.4 ±â€¯1.5%), Spirobranchus kraussii (9.3 ±â€¯1.3%), Saccostrea cucullata (7.6 ±â€¯1.3%) and the barnacle Microeuraphia permitini (5.8 ±â€¯0.9%). Despite the significant difference in coverage of rafting species on plastic items among different sites, there was no clear and consistent trend of species richness and coverage from the eastern (Strait of Hormuz) to the western part of the Persian Gulf. Some rafting species (bryozoans and likely barnacles) were found to be non-indigenous species in the area. As floating marine debris can transport non-indigenous species and increase the risk of bio-invasions to this already naturally- and anthropogenically-stressed water body, comprehensive monitoring efforts should be made to elucidate the vectors and arrival of new invasive species to the region.

The influence of human activity and morphological characteristics of beaches on plastic debris distribution along the Caspian Sea as a closed water body.

The Caspian Sea is the largest land-locked lake in the world that includes numerous endemic species. Because of its enclosed nature, the pollutants entering this water body become entrapped. The present paper examines the influence of human activity and beach morphology on the abundance and distribution of stranded plastic debris along the Caspian Sea coastlines. It would be possible by relating some characteristics of these beaches (population, urbanization, substrate type, and slope of beaches) with the abundance of plastic debris through a PCo analysis. The results showed that in our study area, the most effective factors on plastic debris distribution were urbanization and population followed by the slope and substrate of beaches. Three size classes of plastic debris were defined as "large microplastic" (1 to < 5 mm), "mesoplastic" (5 to < 25 mm), and "macroplastic" (> 25 mm). The density of the large microplastic, mesoplastic, and macroplastic materials on the Caspian Sea coastline was 8.43 ± 0.54, 8.74 ± 0.42, and 7.53 ± 0.30 particles/m2, respectively. Foam was the most abundant microplastic debris along the study area (47.58%), followed by resin pellets (33.93%) and fragments (16.30%), respectively. We also selected the Boujagh National Park with limited accessibility as an appropriate area for the study of marine debris as one sampling station. Cigarette butts and film pieces displayed a different distribution pattern compared to other debris types in the Boujagh National Park station likely due to their distinct buoyancy specification.

Shared Epizoic Taxa and Differences in Diatom Community Structure Between Green Turtles (Chelonia mydas) from Distant Habitats.

The first reports of diatoms growing on marine mammals date back to the early 1900s. However, only recently has direct evidence been provided for similar associations between diatoms and sea turtles. We present a comparison of diatom communities inhabiting carapaces of green turtles Chelonia mydas sampled at two remote sites located within the Indian (Iran) and Atlantic (Costa Rica) Ocean basins. Diatom observations and counts were carried out using scanning electron microscopy. Techniques involving critical point drying enabled observations of diatoms and other microepibionts still attached to sea turtle carapace and revealed specific aspects of the epizoic community structure. Species-poor, well-developed diatom communities were found on all examined sea turtles. Significant differences between the two host sea turtle populations were observed in terms of diatom abundance and their community structure (including growth form structure). A total of 12 and 22 diatom taxa were found from sea turtles in Iran and Costa Rica, respectively, and eight of these species belonging to Amphora, Chelonicola, Cocconeis, Navicula, Nitzschia and Poulinea genera were observed in samples from both locations. Potential mechanisms of diatom dispersal and the influence of the external environment, sea turtle behaviour, its life stage, and foraging and breeding habitats, as well as epibiotic bacterial flora on epizoic communities, are discussed.

Population and life-stage specific sensitivities to temperature and salinity stress in barnacles.

Temperature and salinity shape the distribution and genetic structure of marine communities. Future warming and freshening will exert an additional stress to coastal marine systems. The extent to which organisms respond to these shifts will, however, be mediated by the tolerances of all life-stages and populations of species and their potential to adapt. We investigated nauplius and cypris larvae of the barnacle Balanus (Amphibalanus) improvisus from the Swedish west coast with respect to temperature (12, 20, and 28 °C) and salinity (5, 15, and 30) tolerances. Warming accelerated larval development and increased overall survival and subsequent settlement success. Nauplii developed and metamorphosed best at intermediate salinity. This was also observed in cypris larvae when the preceding nauplii stages had been reared at a salinity of 30. Direct comparisons of the present findings with those on a population from the more brackish Baltic Sea demonstrate contrasting patterns. We conclude that i) B. improvisus larvae within the Baltic region will be favoured by near-future seawater warming and freshening, that ii) salinity tolerances of larvae from the two different populations reflect salinities in their native habitats, but are nonetheless suboptimal and that iii) this species is generally highly plastic with regard to salinity.

A protective coat of microorganisms on macroalgae: inhibitory effects of bacterial biofilms and epibiotic microbial assemblages on barnacle attachment.

Effects of epibiotic bacteria associated with macroalgae on barnacle larval attachment were investigated. Eight bacterial isolates obtained from samples of three macroalga species were cultured as monospecies bacterial films and tested for their activity against barnacle (Amphibalanus improvisus) attachment in field experiments (Western Baltic Sea). Furthermore, natural biofilm communities associated with the surface of the local brown alga, Fucus vesiculosus, which were exposed to different temperatures (5, 15 and 20 °C), were harvested and subsequently tested. Generally, monospecies bacterial biofilms, as well as natural microbial assemblages, inhibited barnacle attachment by 20-67%. denaturing gradient gel electrophoresis fingerprints showed that temperature treatment shifted the bacterial community composition and weakened the repellent effects at 20 °C. Repellent effects were absent when settlement pressure of cyprids was high. Nonviable bacteria tended to repel cyprids when compared to the unfilmed surfaces. We conclude that biofilms can have a repellent effect benefiting the host by preventing heavy fouling on its surface. However, severe settlement pressure, as well as stressful temperature, may reduce the protective effects of the alga's biofilm. Our results add to the notion that the performance of F. vesiculosus may be reduced by multiple stressors in the course of global warming.

Larval settlement of the barnacle, Balanus improvisus Darwin (1854) under different food concentration, substratum, light period, salinity, cyprid density and cyprid age.

The effect of different food concentration, substratum, light periodicity, salinity, cyprid density and cyprid age on the settlement of Balanus improvisus were studies. Released larvae were mass reared in 0.6 L glass beakers to the cyprid stage. Then, attachment was monitored once a day. Chaetoceros calcitrans was used as food at three cell concentrations (0.5 x 10(5), 1 x 10(5) and 2 x 10(5) cells mL(-1)). Larval settlement was carried out on two substratum under three light period (12L:12D, 16L:8D and 8L:16D) at seven salinities (7, 12, 15, 18, 25, 28 and 36 ppt). Cyprid density was used from five to 200 larvae per 5 mL of seawater. Cyprids were aged for one to seven days. The maximum and minimum percent settlement was observed at 2 x 10(5) and 0.5 x 10(5) cells mL(-1), respectively. Cyprids settled in higher numbers on polystyrene compared to glass surface. Percent settlement was higher in 8L:16D than another light periods but, no significant difference in percent settlement between 12L:12D and 16L:8D light periods was seen. Differences in settlement at various salinities were not statistically significant except in 10 ppt which percent settlement was significantly higher. Cyprid density did not have any effect on percent settlement but cyprid age had a significant effect on percent settlement.