Interactive effects of temperature and salinity on metabolism and activity of the copepod Tigriopus californicus.

In natural environments, two or more abiotic parameters often vary simultaneously, and interactions between co-varying parameters frequently result in unpredictable, non-additive biological responses. To better understand the mechanisms and consequences of interactions between multiple stressors, it is important to study their effects on not only fitness (survival and reproduction) but also performance and intermediary physiological processes. The splash-pool copepod Tigriopus californicus tolerates extremely variable abiotic conditions and exhibits a non-additive, antagonistic interaction resulting in higher survival when simultaneously exposed to high salinity and acute heat stress. Here, we investigated the response of T. californicus in activity and oxygen consumption under simultaneous manipulation of salinity and temperature to identify whether this interaction also arises in these sublethal measures of performance. Oxygen consumption and activity rates decreased with increasing assay salinity. Oxygen consumption also sharply increased in response to acute transfer to lower salinities, an effect that was absent upon transfer to higher salinities. Elevated temperature led to reduced rates of activity overall, resulting in no discernible impact of increased temperature on routine metabolic rates. This suggests that swimming activity has a non-negligible effect on the metabolic rates of copepods and must be accounted for in metabolic studies. Temperature also interacted with assay salinity to affect activity, and with acclimation salinity to affect routine metabolic rates upon acute salinity transfer, implying that the sublethal impacts of these co-varying factors are also not predictable from experiments that study them in isolation.

Ice in the intertidal: patterns and processes of freeze tolerance in intertidal invertebrates.

Many intertidal invertebrates are freeze tolerant, meaning that they can survive ice formation within their body cavity. Freeze tolerance is a fascinating trait, and understanding its mechanisms is important for predicting the survival of intertidal animals during extreme cold weather events. In this Review, we bring together current research on the ecology, biochemistry and physiology of this group of freeze-tolerant organisms. We first introduce the ecology of the intertidal zone, then highlight the strong geographic and taxonomic biases within the current body of literature on this topic. Next, we detail current knowledge on the mechanisms of freeze tolerance used by intertidal invertebrates. Although the mechanisms of freeze tolerance in terrestrial arthropods have been well-explored, marine invertebrate freeze tolerance is less well understood and does not appear to work similarly because of the osmotic differences that come with living in seawater. Freeze tolerance mechanisms thought to be utilized by intertidal invertebrates include: (1) low molecular weight cryoprotectants, such as compatible osmolytes and anaerobic by-products; (2) high molecular weight cryoprotectants, such as ice-binding proteins; as well as (3) other molecular mechanisms involving heat shock proteins and aquaporins. Lastly, we describe untested hypotheses, methods and approaches that researchers can use to fill current knowledge gaps. Understanding the mechanisms and consequences of freeze tolerance in the intertidal zone has many important ecological implications, but also provides an opportunity to broaden our understanding of the mechanisms of freeze tolerance more generally.

Cost-efficient PCR based DNA barcoding of marine invertebrate specimens with NovaSeq amplicon sequencing.

BACKGROUND: The marine environment harbors high biodiversity; however, it is poorly understood. Nucleotide sequence data of all marine organisms should be accumulated before natural and/or anthropogenic environmental changes jeopardize the marine environment. In this study, we report a cost-effective and easy DNA barcoding method. This method can be readily adopted without using library preparation kits. It includes multiplex PCR of short targets, indexing PCR, and outsourcing to a sequencing service using the NovaSeq system. METHODS AND RESULTS: We targeted four mitochondrial genes [cytochrome c oxidase subunit I (COI), COIII, 16S rRNA (16S), and 12S rRNA (12S)] and three nuclear genes [18S rRNA (18S), 28S rRNA (28S), internal transcribed spacer 2 (ITS2)] in 95 marine invertebrate specimens, which were primarily annelids. The primers, including adapters and indices for NovaSeq sequencing, were newly designed. Two PCR runs were conducted. The 1st PCR amplified specific loci with universal primers and the 2nd added sequencing adapters and indices to the 1st PCR products. The gene sequences obtained from the FASTQ files were subjected to BLAST search and phylogenetic analyses. One run using 95 specimens yielded sequences averaging 2816 bp per specimen for a total length of six loci. Nuclear genes were more successfully assembled compared with mitochondrial genes. A weak but significantly negative correlation was observed between the average length of each locus and success rate of the assembly. Some of the sequences were almost identical to the sequences obtained from specimens collected far from Japan, indicating the presence of potentially invasive species identified for the first time. CONCLUSIONS: We obtained gene sequences efficiently using next-generation sequencing rather than Sanger sequencing. Although this method requires further optimization to increase the success rate for some loci, it is used as a first step to select specimens for further analyses by determining the specific loci of the targets.

Description of Fuscovulum ytuae sp. nov, a facultative autotroph isolated from the intertidalite of Yangma island, China.

In this study, we reported a Gram-stain-negative, ovoid to rod-shaped, atrichous, and facultative anaerobe bacteria strain named YMD61T, which was isolated from the intertidal sediment of Yangma island, China. Growth of strain YMD61T occurred at 10.0-45.0 °C (optimum, 30.0 °C), pH 7.0-10.0 (optimum, 8.0) and with 0-3.0% (w/v) NaCl (optimum, 2.0%). Phylogenetic tree analysis based on 16 S rRNA gene or genomic sequence indicated that strain YMD61T belonged to the genus Fuscovulum and was closely related to Fuscovulum blasticum ATCC 33,485T (96.6% sequence similarity). Genomic analysis indicated that strain YMD61T contains a circular chromosome of 3,895,730 bp with DNA G + C content of 63.3%. The genomic functional analysis indicated that strain YMD61T is a novel sulfur-metabolizing bacteria, which is capable of fixing carbon through an autotrophic pathway by integrating the processes of photosynthesis and sulfur oxidation. The predominant respiratory quinone of YMD61T was ubiquinone-10 (Q-10). The polar lipids of YMD61T contained phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, five unidentified lipids, unidentified aminolipid and unidentified aminophospholipid. The major fatty acids of strain YMD61T contained C18:1ω7c 11-methyl and summed feature 8 (C18:1 ω 7c or/and C18:1 ω 6c). Phylogenetic, physiological, biochemical and morphological analyses suggested that strain YMD61T represents a novel species of the genus Fuscovulum, and the name Fuscovulum ytuae sp. nov. is proposed. The type strain is YMD61T (= MCCC 1K08483T = KCTC 43,537T).

Thalassospira aquimaris sp. nov. and Winogradskyella marincola sp. nov. two marine bacteria isolated from an agar-degrading co-culture.

Two novel Gram-stain-negative, aerobic, and non-motile strains, designated FZY0004T and YYF002T, were isolated from an agar-degrading co-culture, which was obtained from seawater of the intertidal zone of Yancheng City, the Yellow Sea of China. Strain FZY0004T optimally grew at 28 °C, pH 7.0, and 2-6% NaCl, while strain YYF002T optimally grew at 28 °C, pH 7.5, and 2-4% NaCl. Strain FZY0004T possessed Q-9 as the major respiratory quinone, and its major fatty acids (> 10%) were summed feature 8 (C18:1 ω7c), C16:0, and summed feature 3 (C16:1 ω7c/C16:1 ω6c). The polar lipids identified in strain FZY0004T were phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and several unidentified phospholipids (PL) and lipids (L). On the other hand, strain YYF002T had MK-6 as the predominant respiratory quinone and its major fatty acids consisted of iso-C15:0, iso-C15:1 G, and iso-C15:0 3-OH. The polar lipids identified in strain YYF002T were aminolipid (AL), PE, and several unidentified lipids. Strain FZY0004T shared 99.5% 16S rRNA gene sequence similarity and 90.1% average nucleotide identity (ANI) with T. povalilytica Zumi 95T, and strain YYF002T shared 99.2% 16S rRNA gene sequence similarity and 88.2% ANI with W. poriferorum JCM 12885T. The genomic DNA G + C contents of strains FZY0004T and YYF002T were 54.5% and 33.5%, respectively. The phylogenetic, phenotypic, and physiological characteristics permitted the distinction of the two strains from their neighbors, and we thus propose the names Thalassospira aquimaris sp. nov. (type strain FZY0004T = JCM 35895T = MCCC 1K08380T) and Winogradskyella marincola sp. nov. (type strain YYF002T = JCM 35950T = MCCC 1K08382T).

Occurrence and migration patterns of microplastics in different tidal zones of tourist beaches: A case study in the Bohai Bay, North China.

Coastal areas are acknowledged to be significant reservoirs of microplastics, while limited research on their presence and migration in the intertidal zones. This study investigated in a tourist beach in northern China, to reveal the occurrence of microplastics at different intertidal heights, elucidates their migration patterns, and discusses the impact of tourist activities on microplastics. Results showed that the mean microplastic abundance was 2114.8 ± 933.2 items/kg in sediments and 30,670.8 ± 15,094.9 items/m3 in seawater. Fibers were the most common shape; transparent, blue, green and black prevailed in color; and cellulose and PET were the most common components. Microplastic abundances decreased from high tide zone to low tide zone, and the abundances of microplastics in seawater were positively correlated with those in the high tide zone and negatively correlated with those in the low tide zone. Compared to wave disturbance, human activities have a relatively limited impact on microplastic abundance. However, intensive tourist activities contribute to a higher diversity of microplastic types on tourist beaches. This study enhances the understanding of the occurrence and migration patterns of microplastics in tourist beaches, and provides a valuable dataset and theoretical basis for subsequent research on microplastic pollution in coastal areas.

Adaptation to a new environment with pre-adaptive genomic features - Evidence from woody plants colonizing the land-sea interface.

Adaptation to new environments is a key evolutionary process which presumably involves complex genomic changes. Mangroves, a collection of approximately 80 woody plants that have independently invaded intertidal zones >20 times, are ideal for studying this process. We assembled near-chromosome-scale genomes of three Xylocarpus species as well as an outgroup species using single-molecule real-time sequencing. Phylogenomic analysis reveals two separate lineages, one with the mangrove Xylocarpus granatum and the other comprising a mangrove Xylocarpus moluccensis and a terrestrial Xylocarpus rumphii. In conjunction with previous studies, we identified several genomic features associated with mangroves: (i) signals of positive selection in genes related to salt tolerance and root development; (ii) genome-wide elevated ratios of non-synonymous to synonymous substitution relative to terrestrial relatives; and (iii) active elimination of long terminal repeats. These features are found in the terrestrial X. rumphii in addition to the two mangroves. These genomic features, not being strictly mangrove-specific, are hence considered pre-adaptive. We infer that the coastal but non-intertidal habitat of X. rumphii may have predisposed the common ancestor to invasion of true mangrove habitats. Other features including the preferential retention of duplicated genes and intolerance to pseudogenization are not found in X. rumphii and are likely true adaptive features in mangroves. In conclusion, by studying adaptive shift and partial shifts among closely related species, we set up a framework to study genomic features that are acquired at different stages of the pre-adaptation and adaptation to new environments.

Extreme heatwave drives topography-dependent patterns of mortality in a bed-forming intertidal barnacle, with implications for associated community structure.

Heatwave frequency and intensity will increase as climate change progresses. Intertidal sessile invertebrates, which often form thermally benign microhabitats for associated species, are vulnerable to thermal stress because they have minimal ability to behaviourally thermoregulate. Understanding what factors influence the mortality of biogenic species and how heatwaves might impact their ability to provide habitat is critical. Here, we characterize the community associated with the thatched barnacle, Semibalanus cariosus (Pallass, 1788), in British Columbia (BC), Canada. Then, we investigate what site-level and plot-level environmental factors explained variations in barnacle mortality resulting from an unprecedented regional heatwave in BC, Canada. Furthermore, we used a manipulative shading experiment deployed prior to the heatwave to examine the effect of thermal stress on barnacle survival and recruitment and the barnacle-associated community. We identified 50 taxa inhabiting S. cariosus beds, with variations in community composition between sites. Site-scale variables and algal canopy cover did not predict S. cariosus mortality, but patch-scale variation in substratum orientation did, with more direct solar irradiance corresponding with higher barnacle mortality. The shading experiment demonstrated that S. cariosus survival, barnacle recruitment, and invertebrate community diversity were higher under shades where substratum temperatures were lower. Associated community composition also differed between shaded and non-shaded plots, suggesting S. cariosus was not able to fully buffer acute thermal stress for its associated community. While habitat provisioning by intertidal foundation species is an important source of biodiversity, these species alone may not be enough to prevent substantial community shifts following extreme heatwaves. As heatwaves become more frequent and severe, they may further reduce diversity via the loss of biogenic habitat, and spatial variation in these impacts may be substantial.

Aestuariibaculum lutulentum sp. nov., a marine bacterium isolated from coastal sediment in Beihai.

A Gram-stain negative, strictly aerobic, and rod-shaped bacterium, designated as strain L182T, was isolated from coastal sediment in Beihai, Guangxi Province, PR China. Colonies of strain L182T were yellow, 2 mm in diameter, round, opaque, smooth and convex after incubation on marine ager at 30 °C for 3 days. Cells were catalase-positive but oxidase-negative. Growth of strain L182T was observed at 4-40 °C (optimum, 25 °C), pH 5.5-10.0 (optimum, pH 5.5-8.0) and with 0-6% (w/v) NaCl (optimum, 0.5-4.0%). The G + C content based on the genome sequence was 36.0%. The only respiratory quinone was MK-6. The main polar lipids included phosphatidylethanolamine, phosphatidylglycerol, one unidentified aminophospholipid, one unidentified glycolipids, four unidentified aminolipids and six unidentified lipids. The major fatty acids (> 10%) were iso-C15:0, iso-C15:1 G and iso-C17:0 3-OH. The 16S rRNA gene sequence similarity between strain L182T and Aestuariibaculum suncheonense SC17T was 98.2%, and the similarities with other type strains of the genus Aestuariibaculum were 96.1-97.2%. The average nucleotide identity and in silicon DNA-DNA hybridization values between the strain L182T and its closely related Aestuariibaculum species were 80.8-85.2% and 22.0-29.5%. According to the above results, Aestuariibaculum lutulentum sp. nov. was proposed as a novel species. The type strain is L182T (= MCCC 1K08065T = KCTC 92530T).

Oxidative stress effects are not correlated with differences in heat tolerance among congeners of Mytilus.

The physiological mechanisms that limit thermal tolerance are broadly relevant to comparative biology and global change. Species differences in macromolecular stability play important roles in evolved patterns of heat tolerance, but other mechanisms such as oxidative stress have also been hypothesized to contribute. For example, mussels in the genus Mytilus exhibit evolved physiological differences at several levels of organization that have been linked with interspecific differences in whole-organism heat tolerance. Both omics and behavioral studies suggested that variation in resistance to oxidative stress plays a role in these differences. Functional data are needed to test this hypothesis. Here, we compared three Mytilus congeners to examine whether susceptibility to oxidative stress contributes to acute heat tolerance. We assayed the activity of two antioxidant enzymes (catalase, superoxide dismutase), as well as levels of oxidative damage to lipids, DNA and individual proteins (using gel-based proteomics methods). In addition, we assessed these oxidative stress responses after repeated episodes of heat stress experienced in air or while immersed in seawater, given that survival and competitive outcomes between Mytilus congeners differ in these two contexts. The results are generally inconsistent with patterns that would be expected if oxidative stress contributes to thermal sensitivity. Rather, the more heat-tolerant congeners suffer comparable or even elevated levels of oxidative damage. As predicted, different treatment contexts led to distinct changes in proteome-wide abundance patterns and, to a lesser extent, protein carbonylation profiles. Overall, the results question the relevance of oxidative damage as a mediator of heat tolerance in this genus.

Kaistella polysaccharea sp. nov., isolated from Antarctic intertidal sediment produces a novel extracellular polymeric substance.

An exopolysaccharide-producing bacterial strain GW4-15T, belonging to the genus Kaistella, was isolated from intertidal sediment from King George Island, Antarctic. The strain was Gram-stain-negative, aerobic, rod-shaped, non-motile and yellow-pigmented. The strain was able to grow in the presence of 0-2 % (w/v) NaCl (optimum, 0 %), at 4-30 °C (optimum, 20-28 °C) and at pH 5.0-10.0 (optimum, pH 8.0). A phylogenetic tree based on 16S rRNA gene sequences showed that strain GW4-15T formed a lineage within the genus Kaistella with the closest phylogenetic neighbours Kaistella carnis NCTC 13525T (98.3 %), Kaistella gelatinilytica G5-32T (97.7 %), Kaistella antarctica LMG 24720T (97.4 %) and Kaistella yonginensis HMD1043T (96.9 %). Digital DNA-DNA hybridization values of strain GW4-15T with K. carnis NCTC 13525T, K. antarctica LMG 24720T, K. gelatinilytica G5-32T and K. yonginensis HMD1043T were 22.8, 22.0, 21.7 and 21.6 %, respectively. The average nucleotide identity values between strain GW4-15T and K. carnis NCTC 13525T , K. antarctica LMG 24720T, K. gelatinilytica G5-32T and K. yonginensis HMD1043T were 79.3, 78.6, 77.5 and 77.2 %, respectively. The G+C content of the genome was 36.2 mol%. The major phospholipids were phosphatidylethanolamine and aminophospholipid. The predominant menaquinone was MK-6. The major fatty acids were anteiso-C15 : 0 (28.7 %), iso-C16 : 0 3-OH (15.7 %), iso-C16 : 0 H (10.0 %), iso-C16 : 0 (5.4 %), summed feature 9 (comprising iso-C17 : 1 ω9c and/or 10-methyl C16 : 0; 5.2 %) and iso-C15 : 0 (5.1 %). The monosaccharide composition of the new type of extracellular polymeric of GW4-15T was Glc, GalN, GlcN, Rha, Man and Gal with a molar ratio of 3.14 : 3.83 : 8.38 : 5.16 : 1 : 2.82. Based on phenotypic, phylogenetic and genotypic data, a novel species, Kaistella polysaccharea sp. nov., is proposed with the type strain GW4-15T (=CGMCC 1.19368T=KCTC 92753T).

Origin, Selection, and Succession of Coastal Intertidal Zone-Derived Bacterial Communities Associated with the Degradation of Various Lignocellulose Substrates.

Terrestrial microbial consortia were reported to play fundamental roles in the global carbon cycle and renewable energy production through the breakdown of complex organic carbon. However, we have a poor understanding of how biotic/abiotic factors combine to influence consortia assembly and lignocellulose degradation in aquatic ecosystems. In this study, we used 96 in situ lignocellulose enriched, coastal intertidal zone-derived bacterial consortia as the initial inoculating consortia and developed 384 cultured consortia under different lignocellulose substrates (aspen, pine, rice straw, and purified Norway spruce lignin) with gradients of salinity and temperature. As coastal consortia, salinity was the strongest driver for assembly, followed by Norway spruce lignin, temperature, and aspen. Moreover, a conceptual model was proposed to demonstrate different succession dynamics between consortia under herbaceous and woody lignocelluloses. The succession of consortium under Norway spruce lignin is greatly related with abiotic factors, while its substrate degradation is mostly correlated with biotic factors. A discrepant pattern was observed in the consortium under rice straw. Finally, we developed four groups of versatile, yet specific consortia. Our study not only reveals that coastal intertidal wetlands are important natural resources to enrich lignocellulolytic degrading consortia but also provides insights into the succession and ecological function of coastal consortium.

First report of the mitogenome of the invasive reef-building polychaete Ficopomatus enigmaticus (Annelida: Serpulidae) and a cryptic lineage from the Japanese Archipelago.

BACKGROUND: The mitochondrial genomes (mitogenomes) of the family Serpulidae are characterized by a high nucleotide sequence divergence and a significant number of gene order rearrangements compared with other families within the phylum Annelida. However, only two of 50 genera of serpulids have mitogenomes already sequenced. In this study, we report the first sequencing and assembly of the complete mitogenome of Ficopomatus, thus providing further knowledge on mitochondrial gene sequences of Serpulidae. METHODS AND RESULTS: A mitogenome of the invasive reef-building polychaete Ficopomatus enigmaticus was amplified by long PCR and sequenced using the Illumina MiSeq System. It comprised 15,853 bp and consisted of 12 protein-coding genes (atp8 was not found), 23 tRNA, and two rRNA genes. The AT and GC skew values were infrequent when compared to annelid mitogenomes but similar to other serpulids sequenced to date (i.e., Spirobranchus and Hydroides). The mitochondrial gene order of F. enigmaticus was highly rearranged compared to other serpulids. To amplify 16S rRNA gene sequences, we developed a 16S rRNA primer set by modifying the universal primer set 16SarL/16SbrH. We detected the 16S rRNA sequence of F. enigmaticus deposited in GenBank erroneously characterized as of serpulid origin. We reported for the first time the presence of two lineages of F. enigmaticus in Japan, which have already been identified in California, Australia, and the Mediterranean. CONCLUSIONS: The first mitochondrial genome of F. enigmaticus showed a unique gene order rearrangement, corroborating the remarkable diversity in the previously reported mitogenomes of other serpulid species. The presence of the two lineages of F. enigmaticus identified for the first time in Japan represents another case of cryptic invasion. The first 16S rRNA gene sequences of F. enigmaticus obtained in the present study can be used as reference sequences in future DNA metabarcoding studies.

Populations of the Intertidal Crab Macrophthalmus banzai are Not Grouped by Latitude: Taiwan Population is Genetically Closer to the Populations in the Japanese Mainland Than the Ryukyu Islands.

Macrophthalmus banzai is an intertidal crab species of Macrophthalmidae inhabiting muddy tidal flats in the northwestern Pacific. A previous study on the population genetic structure of Japanese M. banzai based on the mitochondrial COI gene sequences revealed the presence of two genetically distinguished groups, i.e., the northern group (Honshu, Shikoku, and Kyushu Islands) and the southern group (the Ryukyu Islands). In the present study, we newly determined the COI gene sequences of M. banzai collected from Taiwan and conducted population genetic analyses of these sequences together with Japanese sequences obtained from GenBank to reveal the genetic relationship of this species between Japan and Taiwan. The SAMOVA and pairwise ΦST analysis showed that the Taiwan population is more closely related to the northern group than the southern group. This indicates that the populations of M. banzai are not genetically differentiated by latitude but probably by the pathway of the Kuroshio Current, resulting in the isolation of the population in the Ryukyu Islands. Such a pattern is consistent with the population genetic structure of the fiddler crab Tubuca arcuata shown by a previous study, whereas the pattern differs from those of other intertidal invertebrates. The difference in the larval durations may have influenced the difference in population genetic structures among species. The present study provides a further case of the genetic structure of intertidal species that are not simply regulated by geographic distances.

Tropicibacter oceani sp. nov., a novel sulfur-metabolizing bacteria isolated from the intertidal zone sediment of Chinese Yellow Sea.

In this study, we reported a Gram-stain-negative, rod-shaped, atrichous, and aerobic bacterial strain named YMD87T, which was isolated from the intertidal zone sediment of Chinese Yellow Sea. Growth of strain YMD87T occurred at 10.0-40.0 °C (optimum, 25-30 °C), pH 4.0-12.0 (optimum, 8.0) and with 0-6.0% (w/v) NaCl (optimum, 0.0-2.0%). Phylogenetic tree analysis based on 16S rRNA gene sequence indicated that strain YMD87T belonged to the genus Tropicibacter and was closely related to Tropicibacter alexandrii LMIT003T (97.2% sequence similarity). Genomic analysis indicated that strain YMD87T contains a circular chromosome of 3,932,460 bp with G + C content of 63.8% and three circular plasmids of 116,492 bp, 49,209 bp and 49,673 bp, with G + C content of 64.3%. Genomic functional analysis revealed that strain YMD87T is potential a novel sulfur-metabolizing bacteria. The predominant respiratory quinone of YMD87T was ubiquinone-10 (Q-10). The major polar lipids of YMD87T contained phosphatidylglycerol, phosphatidylethanolamine, five unidentified lipids, five unidentified phospholipids, phosphatidylcholine, unidentified glycolipid and five unidentified aminolipids. The major fatty acids of strain YMD87T contained C12:1 3-OH, C16:0, and summed feature 8 (C18:1 ω7c or/and C18:1 ω6c). Phylogenetic, physiological, biochemical and morphological analyses suggested that strain YMD87T represents a novel species of the genus Tropicibacter, and the name Tropicibacter oceani sp. nov is proposed. The type strain is YMD87T (= MCCC 1K08473T = KCTC 92856 T).

Surviving hot summer: Roles of phenotypic plasticity of intertidal mobile species considering microhabitat environmental heterogeneity.

For species inhabiting warming and variable thermal environment, coordinated changes in heat tolerance to temperature fluctuations, which largely depend on phenotypic plasticity, are pivotal in buffering high temperatures. Determining the roles of phenotypic plasticity in wild populations and common garden experiments help us understand how organisms survive hot summer and the warming world. We thus monitored the operative temperature of the intertidal limpets Cellana toreuma in both emergent rock and tidal pool microhabitats from June to October 2021, determined the variations of upper thermal limits of short-term acclimated and long-term acclimated limpets from different microhabitats (emergent rock and tidal pool), and further calculated the relationship between the upper thermal limits and acclimation capacity. Our results indicated that living on the emergent rock, limpets encountered more extreme events in summer. For the short-term acclimated samples, limpets on the emergent rock exhibited obvious variations of sublethal thermal limit (i.e., Arrhenius Break Point of cardiac performance, ABT) during summer months, however, this variation of ABT was absent in the limpets in the tidal pool. After the laboratory long-term acclimation, the ABTs and FLTs (Flat Line Temperature of cardiac performance, as an indicator of lethal temperature) of limpets both on the rock and in the tidal pool increased significantly in October, implying the potential existence of selection during the hot summer. Our results further showed that environmental temperature was an important driver of phenotypic plasticity. This study highlighted the changes in the thermal tolerance of intertidal limpets during summer in different microhabitats.

Lethal and sublethal implications of low temperature exposure for three intertidal predators.

Benthic invertebrate predators play a key role in top-down trophic regulation in intertidal ecosystems. While the physiological and ecological consequences of predator exposure to high temperatures during summer low tides are increasingly well-studied, the effects of cold exposure during winter low tides remain poorly understood. To address this knowledge gap, we measured the supercooling points, survival, and feeding rates of three intertidal predator species in British Columbia, Canada - the sea stars Pisaster ochraceus and Evasterias troschelii and the dogwhelk Nucella lamellosa - in response to exposure to sub-zero air temperatures. Overall, we found that all three predators exhibited evidence of internal freezing at relatively mild sub-zero temperatures, with sea stars exhibiting an average supercooling point of -2.50 °C, and the dogwhelk averaging approximately -3.99 °C. None of the tested species are strongly freeze tolerant, as evidenced by moderate-to-low survival rates after exposure to -8 °C air. All three predators exhibited significantly reduced feeding rates over a two-week period following a single 3-h sublethal (-0.5 °C) exposure event. We also quantified variation in predator body temperature among thermal microhabitats during winter low tides. Predators that were found at the base of large boulders, on the sediment, and within crevices had higher body temperatures during winter low tides, as compared to those situated in other microhabitats. However, we did not find evidence of behavioural thermoregulation via selective microhabitat use during cold weather. Since these intertidal predators are less freeze tolerant than their preferred prey, winter low temperature exposures can have important implications for organism survival and predator-prey dynamics across thermal gradients at both local (habitat-driven) and geographic (climate-driven) scales.

Geographic distance, sedimentation, and substrate shape cryptic crustose coralline algal assemblages in the world's largest subtropical intertidal algal reef.

Algal reefs, concreted by crustose coralline algae (CCA), are the main biotic reefs in temperate waters but rare in the subtropics and tropics. The world's largest known intertidal algal reef in the subtropics is the Taoyuan Algal Reef (TAR) located in the northwestern coast of Taiwan. The biodiversity and ecology of the TAR are scarcely explored, and now the reef is imperiled by industrialization. Here, we document cryptic species of CCA in Taiwan, particularly the TAR, by sequencing the psbA genes of over 1800 specimens collected across Taiwan. We also examine the ecological background of the TAR by surveying its benthic composition and measuring its environmental parameters. Our data reveal that the TAR harbours a high diversity of cryptic CCA species (27 molecular operational taxonomic units, or mOTUs), many of which are potentially new to science (18 mOTUs) and/or endemic to the TAR (9 mOTUs). Comparing the CCA species inventory of the TAR with the rest of Taiwan shows that the TAR represents a unique hotspot of CCA taxa in the waters of Taiwan. Our analyses show that variation in the CCA assemblages in the TAR is associated with geographic distance, sedimentation, and substrate type (for example, reef vs. hermit crab shell), suggesting that dispersal limitation and contemporary environmental selection shape the CCA assemblages in the TAR. The data from this study can inform the monitoring of human impacts on the health of the TAR and contribute to our understanding of the ecological processes underlying algal reef development.

Bioremediation of Petroleum Hydrocarbons in the Upper Parts of Sandy Beaches.

The biodegradation of dispersed crude oil in the ocean is relatively rapid (a half-life of a few weeks). However, it is often much slower on shorelines, usually attributed to low moisture content, nutrient limitation, and higher oil concentrations in beaches than in dispersed plumes. Another factor may be the increased salinity of the upper intertidal and supratidal zones because these parts of the beach are potentially subject to prolonged evaporation and only intermittent inundation. We have investigated whether such an increase in salinity has inhibitory effects on oil biodegradation in seashores. Lightly weathered Hibernia crude oil was added to beach sand at 1 or 10 mL/kg, and fresh seawater, at salinities of 30, 90, and 160 g/L, was added to 20% saturation. The biodegradation of oil was slower at higher salinities, where the half-life increased from 40 days at 30 g/L salts to 58 and 76 days at 90 and 160 g/L salts, respectively, and adding fertilizers somewhat enhanced oil biodegradation. Increased oil concentration in the sand, from 1 to 10 mL/kg, slowed the half-life by about 10-fold. Consequently, occasional irrigation with fertilization could be a suitable bioremediation strategy for the upper parts of contaminated beaches. However, dispersing oil at sea is probably the most suitable option for the optimal removal of spilled crude oil from the marine environment.

Variable Optimization of Seaweed Spectral Response Characteristics and Species Identification in Gouqi Island.

Probing the coverage and biomass of seaweed is necessary for achieving the sustainable utilization of nearshore seaweed resources. Remote sensing can realize dynamic monitoring on a large scale and the spectral characteristics of objects are the basis of remote sensing applications. In this paper, we measured the spectral data of six dominant seaweed species in different dry and wet conditions from the intertidal zone of Gouqi Island: Ulva pertusa, Sargassum thunbergii, Chondrus ocellatus, Chondria crassiaulis Harv., Grateloupia filicina C. Ag., and Sargassum fusifarme. The different seaweed spectra were identified and analyzed using a combination of one-way analysis of variance (ANOVA), support vector machines (SVM), and a fusion model comprising extreme gradient boosting (XGBoost) and SVM. In total, 14 common spectral variables were used as input variables, and the input variables were filtered by one-way ANOVA. The samples were divided into a training set (266 samples) and a test set (116 samples) at a ratio of 3:1 for input into the SVM and fusion model. The results showed that when the input variables were the normalized difference vegetation index (NDVI), ratio vegetation index (RVI), Vre, Abe, Rg, Lre, Lg, and Lr and the model parameters were g = 1.30 and c = 2.85, the maximum discrimination rate of the six different wet and dry states of seaweed was 74.99%, and the highest accuracy was 93.94% when distinguishing between the different seaweed phyla (g = 6.85 and c = 2.55). The classification of the fusion model also shows similar results: The overall accuracy is 73.98%, and the mean score of the different seaweed phyla is 97.211%. In this study, the spectral data of intertidal seaweed with different dry and wet states were classified to provide technical support for the monitoring of coastal zones via remote sensing and seaweed resource statistics.