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Effects of sediment on a rocky intertidal habitat-forming species and its harboured invertebrate assemblages
( 2026 ) Veiga, Puri; Torres, Catarina; Sousa Pinto, Isabal; Rubal, Marcos
Sedimentation in rocky shores occurs through natural processes, but it is rising globally due to anthropogenic activities. However, few studies have assessed sediment effects on habitat-forming species and its harboured assemblages. To fill this knowledge gap, the mussel Mytilus galloprovincialis was considered as model habitat-forming to evaluate differences associated with varying sediment loads on mussel density and its invertebrate assemblages harboured. Field data were obtained at two non-urban intertidal rocky shores in the Northern Portuguese coast. First, the relationship between sediment load in mussel clumps and the associated invertebrate assemblages was examined in terms of abundance, richness, Pielou and Shannon indexes and multivariate structure. Then, mussel clumps with low and high sediment load were selected at each rocky shore to test differences on density and size of mussels and assemblage descriptors between them.
Sediment on mussels was composed by very coarse and coarse sand and showed a patchy distribution, but density and size of mussels were unaffected by sediment. Our results suggest significant effects of sediment on invertebrate assemblage associated with mussels specifically, decreasing evenness and heterogeneity of assemblages by favouring species tolerant to sediment (annelids, copepods and nematodes) and reducing the abundance of grazers and Nucella lapillus. As grazers and N. lapillus are considered keystone species, changes on them may trigger cascading effects on rocky shore ecosystems.
Our results highlight that even sedimentation derived from natural processes may impact intertidal biodiversity, which should be considered when managing coastal interventions specially in the current global change framework that probably will exacerbate sedimentation.
Back after 43 years: a new species of Actinarctus (Heterotardigrada, Tanarctidae) from the northeast coast of India
( 2026 ) Vishnudattan, Naduvilakkandy; Rubal, Marcos; De, Kalyan
Marine tardigrades from the Indian waters offer an important but largely overlooked component of regional biodiversity, and every new record contributes significantly to understanding their distribution and taxonomy. Expanding knowledge of this group, the present study describes a new species of Actinarctus Schulz, 1935 discovered nearly half a century after the last known addition to the genus, from the coastal region of Odisha along the northeast coast of India. This highlights the hidden diversity of marine meiofauna in the Indian subcontinent. The new species, Actinarctus odissi sp. nov., can be easily distinguished from its congeners by the structure and ornamentation of the dorsal body cuticle, shape and arrangements of lateral epicuticular alae, structure and length of leg IV sensory organ and primary clava, presence of Van der Land’s organ in the cephalic and leg sensory organs, occurrence of two small, circular, cushion-like structures between the bases of the internal and external digits.
Tracing the intruders: a global appraisal of marine invasive species detection through DNA-based approaches
( 2026 ) Duarte, Sofia Alexandra Ferreira; Costa, Filipe O.
Early detection and monitoring of non-indigenous species (NIS) is crucial to prevent their establishment and to reduce ecological and economic impacts in coastal ecosystems. Traditional monitoring approaches, which rely largely on morphological identification of collected organisms, are often time-consuming and may fail to detect species that occur at low abundance, are morphologically cryptic, or are present in the form of inconspicuous life stages. DNA-based approaches, particularly those resorting to environmental DNA, have demonstrated high aptitude for biodiversity monitoring and biosecurity surveillance. By examining the genetic material from bulk community samples or released into the environment, DNA-based approaches enable the detection of species without the need for direct observation, thereby increasing detection sensitivity and expanding the scope of monitoring programs. Despite the rapid growth of its employment in marine monitoring, a global synthesis of the status and trends of DNA-based approaches for detecting NIS in this environment has been lacking. Here, we present such synthesis, based on 146 published studies employing DNA for NIS detections in coastal environments. Two main methodological approaches were used across the reviewed studies, namely DNA metabarcoding which was applied in 49% of studies, closely followed by targeted single-species PCR assays, used in 42% of the studies. A smaller proportion of studies (10%) combined both approaches, integrating broad community screening with targeted detection to improve surveillance efficiency. Globally, 752 NIS were detected across disparate taxonomic groups, with metazoans representing the largest proportion of detections (464 species), followed by Chromista (210 species) and Plantae (77 species). Among these, the most frequently detected taxonomic groups included Dinophyceae (Dinoflagellata), Teleostei (Chordata), Florideophyceae (Rodophyta), Polychaeta (Annelida), Copepoda and Malacostraca (Arthropoda), and Ascidiacea (Chordata). At the species level, several well-known marine invaders were recurrently reported, including Bugula neritina (Linnaeus, 1758), Styela plicata (Lesueur, 1823), Acartia (Acanthacartia) tonsa Dana, 1849-1852, and Botryllus schlosseri (Pallas, 1766), highlighting the ability of DNA approaches to detect widespread and established invaders across different regions. The mitochondrial cytochrome c oxidase subunit I (COI) gene was the most widely used genetic marker, reflecting its broad taxonomic coverage and extensive representation in reference databases, particularly for targeting Metazoa. Ribosomal RNA genes, particularly 18S and 16S rRNA gene markers, were also frequently employed to target a wider range of eukaryotic taxa. Regarding sampled substrates, water was by far the most analyzed substrate, followed by zooplankton and biofouling communities collected from man-made structures. Notably, approximately 31% of all NIS detections reported in the reviewed studies constituted new regional records. These results highlight the potential of eDNA for coastal monitoring but also underline important limitations. Persistent geographical, taxonomic, and methodological biases can affect detection outcomes, and reliance on single sample types or markers may increase false negatives - particularly critical for NIS early detection. Therefore, multi-marker and multi-substrate approaches are essential to improve detection reliability and support effective biosecurity strategies. As reference databases continue to expand and methodological protocols become increasingly standardized, DNA-based monitoring is likely to play a central role in future management and surveillance of biological invasions in coastal ecosystems.