Describing species has been a formal, intellectually rich and influential applied and basic area of study for many of the past 260 years. While formally described eukaryotic diversity still falls short of estimated eukaryotic species diversity by many hundreds of thousands of species, some recent accounts have suggested a growing number of taxonomists are within reach of describing all extant species. We present a case study that illustrates, to the contrary, a recent ‘taxonomic impediment’ in part attributable to derogation of taxonomy as a scientific discipline: contemporary practice has re-interpreted taxonomy largely as an endeavour in enumerating species. We argue that challenges lie in (1) a poor understanding of taxonomy's epistemology; (2) excessive displacement of interest toward ecological or molecular studies; (3) over-interpretation of the contributions of multiple authors describing a species; and (4) perspectives that are strongly influenced by well-known taxa. The historical and recent literature on scyphozoans reveal ghosts of taxonomy's past that persist in the present, but suggest also that a renaissance enabled by integrative taxonomy is possible in the (near) future.

The present study provides a comprehensive survey of the planktonic hydrozoan fauna from the Paranaguá Estuarine System (PES; southern Brazil, 25°S 48°W), a subtropical estuary considered a Natural World Heritage site by UNESCO. Extensive collections were performed throughout the estuary in five sampling campaigns during the summer and winter periods of 2012 and 2013 and summer of 2014, totalling 185 samples. About 49,000 organisms were analysed which together with the few previous records resulted in a total of 36 hydromedusae and three siphonophore species. We highlight the presence of Cnidostoma fallax in high abundance (>19,000 individuals captured; ~40% of all planktonic hydrozoans). The high abundance of this species throughout three consecutive summers suggests a change in the local assemblage structure, since previous reports in the 1980s, 1990s and 2000s had shown Liriope tetraphylla recurrently as the dominant species which now ranks fourth. It is difficult to ascertain the causes of such changes due to the paucity of previous studies on Brazilian estuaries, but one possibility is that C. fallax has been recently introduced. In any case, the high dominance of this hydromedusa was not expected and this scenario would potentially cause changes in the local food web since C. fallax and L. tetraphylla are quite different morphologically and ecologically and thus probably play different trophic roles. Future studies are necessary to check the long-term permanency of C. fallax and to assess its biology and ecology and the impact of this assemblage change on the ecosystem.

Feeding, defecation, palp behaviour and motility of the tubicolous annelid, Magelona alleni were observed in a laboratory environment. Both surface deposit, and to a lesser extent, suspension feeding were exhibited, with the ingestion of sand grains, and of smaller amounts of foraminiferans and administered commercially available suspension. Predominantly sand could be seen moving through the gut, resulting in conspicuous defecation, not previously observed in other magelonid species. During this ‘sand expulsion’ behaviour, individuals turned around in a network of branched burrows. The posterior was extended from the burrow and substantial amounts of sand were expelled in a string-like formation, involving mucus. The posterior morphology of M. alleni differs greatly compared with other European magelonid species, in possessing a large terminal anus, likely related to its diet. In contrast to what has been recorded for other magelonids, M. alleni appears predominately non-selective. The current paper adds credence to the idea that multiple feeding modes exist within the family. Tube-lined burrows were observed to be primarily permanent, and motility of the species reduced in comparison to other magelonids. The differences noted between M. alleni and other species is most likely linked to its tubicolous lifestyle. The effect of environmental parameters on observed behaviours is discussed.

The technical difficulties of performing underwater observation mean that marine ecologists have long relied on behavioural experiments to study reactions of marine organisms. In this article, we examine the underlying complexity of assumptions made in raceway experiments and we propose a statistical inference procedure tailored to this type of experimental protocol. As an example, experiments were performed to test if light of two different intensities affects the proximal behaviour (i.e. direct, local and immediate) of two species of crustaceans, the hermit crab (Pagurus bernhardus), and the green crab (Carcinus maenas). Individuals were collected in the vicinity of the Sven Loven Marine Center in Tjarnö (Sweden). Their movements in raceways were recorded and the statistical distance between the resulting experimental distribution and a simulated null distribution was used to compare their behaviour in two situations: dim (when they were expected to feed) and bright light (when they were expected to shelter). Initial tests indicated no differences of behaviour between dim and bright light for the two species. However, when compared with the reference state (here, a null distribution) the behaviour in dim light deviates significantly from the null distribution suggesting non-random behaviour. Our results suggest that efforts should be made to understand the behaviours of the individuals of these two species to establish a comprehensive reference state as a basis for comparison. This fundamental information should be a prerequisite before implementing experiments testing how potential disturbances affect individual organisms in behavioural ecology.

Benthic communities, critical to the health and function of marine ecosystems, are under increasing pressure from anthropogenic impacts such as pollution, eutrophication and climate change. In order to refine predictions of likely future changes in benthic communities resulting from these impacts, we must first better constrain their responses to natural seasonality in environmental conditions. Epibenthic time series data (July 2008–May 2014) have been collected from Station L4, situated 7.25 nautical miles south of Plymouth in the Western English Channel. These data were analysed to establish patterns in community abundance, wet biomass and composition, and to link any observed patterns to environmental variables. A clear response to the input of organic material from phytoplankton blooms was detected, with sediment surface living deposit feeders showing an immediate increase in abundance, while predators and scavengers responded later, with an increase in biomass. We suggest that this response is a result of two factors. The low organic content of the L4 sediment results in food limitation of the community, and the mild winter/early spring bottom water temperatures allow the benthos to take immediate advantage of bloom sedimentation. An inter-annual change in community composition was also detected, as the community shifted from one dominated by the anomuran Anapagurus laevis to one dominated by the gastropod Turitella communis. This appeared to be related to a period of high larval recruitment for T. communis in 2013/2014, suggesting that changes in the recruitment success of one species can affect the structure of an entire community.

Swimming propagules (embryos and larvae) are a critical component of the life histories of benthic marine animals. Larvae that feed (planktotrophic) have been assumed to swim faster, disperse farther and have more complex behavioural patterns than non-feeding (lecithotrophic) larvae. However, a number of recent studies challenge these early assumptions, suggesting a need to revisit them more formally. The current review presents a quantitative analysis of swimming speed and body size in planktotrophic and lecithotrophic propagules across five major marine phyla (Porifera, Cnidaria, Annelida, Mollusca and Echinodermata). Results of the comparative study showed that swimming speed differences among ciliated propagules can be driven by taxonomy, adult mobility (motile vs sessile) and/or larval nutritional mode. On a phylogenetic level, distinct patterns emerge across phyla and life stages, whereby planktotrophic propagules swim faster in some of them, and lecithotrophic propagules swim faster in others. Interestingly, adults with sessile and sedentary lifestyles produce propagules that swam faster than the propagules produced by motile adults. Understanding similarities and differences among marine propagules associated with different reproductive strategies and adult lifestyles are significant from ecological, evolutionary and applied perspectives. Patterns of swimming can directly impact the dispersal/recruitment potential with incidence on the design of larval rearing methods and marine protected areas.

To elucidate the details of both the current status of contamination and the accumulation of organotin compounds (OTs) in mangroves in coastal ecosystems, we determined the concentrations of butyltin compounds (BTs) and phenyltin compounds (PTs) in sediment and mangrove leaves collected from mangrove forests in Merambong and Tinggi Island, Malaysia. Butyltins were detected in all sediment samples collected from both regions, whereas PTs were not detected. The levels of tributyltin (TBT) compounds in the sediment samples were lower than those from previous studies conducted in Malaysia and at other sites in South-east Asia. In both Merambong and Tinggi Island, the average proportions of dibutyltin (DBT) and monobutyltin (MBT), which are degradation products of TBT, were ~70%. This result suggests that the input of TBT has decreased in Malaysia. The proportions of DBT and MBT in the sediment from Merambong were higher than those from Tinggi Island. The concentrations of TBT in mangrove leaves from Tinggi Island were significantly higher than those from Merambong. MBT was the most dominant type among the BTs in mangrove leaves from both Merambong and Tinggi Island. The ratios of the BTs burden in mangrove leaves to the BTs concentration in sediment from Merambong and Tinggi Island averaged 3.1 and 6.2, respectively. Among the values of BTs, the MBT values were found to be the highest in both regions.

Macroalgae play important ecological roles, including as hosts for a wide range of epifauna. However, the diversity relationships between macroalgae and epifauna are poorly understood for most tropical host species and algal morphologies. This study aims to characterize and analyse the diversity of invertebrates present amongst macroalgae with three distinct morphologies (three-dimensional, filamentous and foliose) across different tropical intertidal sites in Singapore. Morphological and DNA barcoding tools were employed for epifaunal species identification, and ordination statistics and multiple linear regression were used to test the effects of algal morphology, species and site on community structure and diversity of epiphytic invertebrates. Overall, epifaunal communities were distinct among sites and algal morphologies, and diversity was affected significantly by algal morphology. In particular, filamentous macroalgae hosted the highest abundance of epifauna dominated mainly by amphipods, which were able to take advantage of the high surface area to volume ratio in filamentous algal mats as a consequence of their thinner forms. Foliose species showed a significantly negative effect on invertebrate diversity. Our findings highlight the diverse associations between intertidal macroalgae and invertebrates with high turnover between algal morphology and sites that contribute to the high biodiversity of tropical shores. Future studies should consider the effects of the host habitat, seasonality and more algal species on epifaunal diversity.

The continued development of the aquaculture industry is contributing to the proliferation of artificial structures in the marine environment. Observations of seaweed farms (infrastructure and biomass) suggest they act as a habitat for associated species. Seaweed farms differ from other forms of artificial infrastructure as the material deployed already has marine organisms (i.e. culture species) growing on it. This ‘priming’ of ropes with juvenile sporophytes may affect future development of communities by facilitating colonizing species or suppressing competitors. We call this process ‘ecological priming’: the provision of a biological platform that influences the successional development of specific communities. The communities that developed on ropes primed with Alaria esculenta individuals were compared with unprimed ropes to assess the ecological priming effect, at a commercial kelp farm in south-west Ireland. Species richness increased over two cultivation seasons and species composition was consistent between years, with distinct communities developing on primed and unprimed treatments. Timing of species occurrence on primed ropes was predictable with no predictable pattern occurring on unprimed ropes. Multivariate tests indicated distinct communities between treatments, with suppression of other algal species and potential facilitation of some species that have a particular association with A. esculenta on primed ropes. Communities from primed holdfasts contained a lower diversity of algal species compared with unprimed communities. Cultivated kelp holdfasts represent a habitat for distinct assemblages that reflect ecological priming of the substratum.

Cosmopolitan habitat-forming taxa of algae such as the genus Corallina provide an opportunity to compare patterns of biodiversity over wide geographic scales. Nematode assemblages inhabiting Corallina turves were compared between the south coasts of the British Isles and South Korea. A fully nested design was used with three regions in each country, two shores in each region and replicate samples taken from three patches on each shore to compare differences in the taxonomic and biological trait composition of nematode assemblages across scales. A biological traits approach, based on functional diversity of nematodes, was used to make comparisons between countries, among regions, between shores and among patches. The taxonomic and biological trait compositions of nematode assemblages were significantly different across all spatial scales (patches, shores, regions and countries). There is greater variation amongst nematode assemblages at the scale of shore than at other spatial scales. Nematode assemblage structure and functional traits are influenced by the local environmental factors on each shore including sea-surface temperature, the amount of sediment trapped in Corallina spp. and tidal range. The sea-surface temperature and the amount of sediment trapped in Corallina spp. were the predominant factors determining nematode abundance and composition of assemblages and their functional diversity.

High definition video from a towed camera system was used to describe the deep-sea benthic habitats within an elongate depression located at the western margin of Rockall Bank in the Hatton–Rockall Basin. At depths greater than 1190 m, an extensive area (10 km long by 1.5 km wide) of what appeared to be reduced sediments, bacterial mats and flocculent matter indicated possible cold-seep habitat. Plumes of sediment-rich fluid were observed alongside raised elongate features that gave topographic relief to the otherwise flat seafloor. In the deepest section of the depression (1215 m) dense flocculent matter was observed suspended in the water column, in places obscuring the seabed. Away from the bacterial mats, the habitat changed rapidly to sediments dominated by tube-dwelling polychaete worms and then to deep-sea sedimentary habitats more typical for the water depth (sponges and burrowing megafauna in areas of gentle slopes, and coral gardens on steeper slopes).

We describe and illustrate a new genus and species of sea anemone from the intertidal in the Gulf of California (Mexico). Tenactis gen. nov. is characterized by mesenteries decamerously arranged, a single pair of directives attached to a single and strong siphonoglyph, small conchula, endodermal marginal sphincter muscle, pedal disc with basilar muscles, cinclides in pedal disc and proximal column, column with verrucae and pseudoacrorhagi, and a cnidom with p-mastigophores A2 and p-mastigophores B1 and B2a. Tenactis riosmenai gen. et sp. nov. is characterized by having a column not divisible into regions with longitudinal rows of verrucae distally and pseudoacrorhagi forming spherical structures at the tip, only 10 pairs of perfect mesenteries, diffuse endodermal marginal sphincter muscle and p-mastigophores A2 and p-mastigophores B1 and B2a in the filaments. Because of the decamerous arrangement of the mesenteries Tenactis gen. nov. most closely resembles some members of Actiniidae, Haloclavidae, Minyadidae, Oractiidae and Limnactinidae (Actinioidea), Halcampidae (Metridioidea) and Halcuriidae (Actinernoidea). However, the combination of having a decamerous arrangement of mesenteries, single siphonoglyph, conchula and cinclides indicate this new genus belongs to Haloclavidae. Additionally, the presence of a diffuse endodermal marginal sphincter muscle, basilar muscles, a single pair of directives, column with longitudinal rows of verrucae distally and pseudoacrorhagi, p-mastigophores A2, and p-mastigophores B1 and B2a in the filaments distinguish Tenactis riosmenai gen. et sp. nov. within Haloclavidae. This is the first record of the family Haloclavidae for the Gulf of California.

The present study aims to assess the environmental quality of six estuaries in north-eastern Brazil, using biochemical composition and quantity of organic matter in tropical sediments. Samples were collected monthly during spring low tide from August 2011 to July 2012, in the mid-littoral. Concentrations of organic matter and its biochemical composition reflected the degree of anthropogenic pressure. Although total concentrations of proteins and carbohydrates were similar among estuaries with contrasting levels of anthropogenic pressure, the protein to carbohydrates (PRT : CHO) ratio effectively reflected the trophic state of these areas. PRT : CHO ratios >1 were observed in all studied areas suggesting eutrophic conditions or an initial stage of eutrophication in all of them. Low Chl-a/Phaeo ratios may be associated with the level of eutrophication of each area, however it may also reflect the natural productivity or the presence of mangrove debris. These results were compared with those obtained in previous environmental assessments of the same estuarine areas using the AZTI Marine Biotic Index and monitoring reports showing good agreement. The present study confirmed for the first time in tropical estuarine areas that the biochemical approach can be successfully used to assess the trophic state of the benthic compartment.

Although necessary for sustainable management of coastal ecosystems the understanding of trophic ecology of kelp fishes remains largely limited in the NE Atlantic. In this paper, stable isotope ratios of carbon (C) and nitrogen (N), complementarily with analyses of stomach contents, were used to investigate the trophic ecology of an Atlantic kelp forest fish assemblage targeted by spear fishers in Galicia (NW Spain). Trophic habits of the fishes were consistent across the species ranges and six trophic niches were identified. Chelon labrosus was the only pelagic omnivore, while Conger conger and Dicentrarchus labrax were the principal predators, preying on benthic osteichthyes. The intermediate carnivorous Diplodus sargus mainly preyed on benthic molluscs, while Labrus bergylta exploited a wider range of prey. Although associated with different trophic niches, the two morphotypes of L. bergylta showed some degree of diet overlap, providing little support to the hypothesis of their separate management. Moreover, L. bergylta can be a keystone species whose adequate management has relevant implications for the sustainable use of the European kelp forest ecosystems.

Mechanized dredging impact on discards was assessed along the northern Alboran Sea (W Mediterranean Sea). Data from 101 dredging operations were analysed for contrasting spatial and seasonal variability of damage, with the use of a three-level damage scale. 4.5% of discarded individuals displayed intermediate damage, whereas 11.3% displayed severe damage. Echinoderms displayed the highest level of damage (~75% of total collected individuals) and Echinocardium cf. mediterraneum was the most susceptible discarded species (85% with severe damage), followed by bivalves (7.3%) and crustaceans (3.3%). The target Chamelea gallina showed a low proportion of damaged individuals, probably due to their thick protective shell, which promotes the survival of discarded undersized target individuals. Spatial differences in damage level on discards were linked to some gear characteristics, to the higher amount of gravels and to longer tow durations, whereas damage was generally higher in cold months and partly related to higher quantities of hard shelled molluscs, in both cases increasing the abrasion and damage to retained organisms. Data suggest that dredges with a lower number of narrower iron teeth and towed for a shorter time could decrease the damage rate in discards of this fishery. A spatial management plan based on the type of grounds would be useful in order to improve efficiency of these fisheries and minimize their impact to soft bottoms with different commercial catches and biological communities.

The Bay of Málaga is located in a high biodiversity and productivity area that harbours a wide variety of commercial species exploited by different fishing fleets. Benthic and demersal fauna from circalittoral soft bottoms have been studied using a benthic dredge (BD) (8 sampling stations) and an otter trawl (OT) (8 sampling stations on a seasonal basis). Some sediment and water column variables, as well as the trawling activity, have also been studied and used for analysing their linkage with the fauna. A total of 287 species have been found in these bottoms and fish, molluscs and crustaceans represented the most diverse and abundant faunistic groups. A new record of the decapod Hippolyte leptometrae for Spanish waters is also included in this study. Some multivariate analyses using BD samples indicated the presence of three assemblages, but these seem to represent different facies of a single benthic community due to the absence of acute sediment changes and significant differences in the fauna. OT samples only displayed differences related to seasons but not to sediment types or depth. These seasonal differences seem to be linked to biological and ecological features of both dominant and/or commercial species. Mud and organic matter contents (%OM) in sediment, as well as the temperature, were the main variables linked to the spatial distribution of the benthic community identified with BD, whereas medium and coarse sand as well as gravel contents were the main variables linked to the changes of the epibenthic and demersal assemblage resulting from OT samples. The information of this study is of importance for improving the knowledge on the biodiversity of circalittoral soft bottoms of the Mediterranean and Alboran Sea as well as for the potential creation of a Marine Fisheries Reserve in the Bay of Málaga.

Reef encrusting calcifiers (non-scleractinian species) constitute assemblages that participate in the carbon cycle at coral reefs. Despite their apparent secondary role in building the reef framework, they contribute to the reef consolidation binding sediments and inducing larval recruitment from other epilithic invertebrates. The contribution of encrusting calcifiers on reef accretion was examined by the assessment of their rate of carbonate deposition on four different simulated reef microhabitats using calcification accretion units (CAUs) during 12 months at Playa Las Gatas and Islote Zacatoso, two coral communities from the coast of the Mexican Pacific. Encrusting calcifiers from Playa Las Gatas, the most impacted site, showed a rate of carbonate deposition (mean ± SD) four times higher than at Islote Zacatoso (10.02 ± 3.22 g CaCO3 m−2 d−1vs 2.48 ± 1.01 g CaCO3 m−2 d−1). Overall, the rate of carbonate deposition on surfaces protected from sedimentation and light was up to 1.8 times higher than on exposed ones (11.40 ± 4.35 g CaCO3 m−2 d−1vs 6.18 ± 3.13 g CaCO3 m−2 d−1). Carbonate deposition by calcareous algae was higher on the well-lit exposed surfaces while filter-feeding invertebrates showed the major contribution on the shaded cryptic surfaces. Although rate of carbonate deposition by encrusting calcifiers seems to be lower than hermatypic corals, it seems to be relevant on coral reefs affected by anthropogenic impacts where coral calcification is low. Under global demise of coral reefs by environmental degradation and climate change, encrusting calcifiers may become relevant for the process of carbonate deposition.