Monitoring Of Benthic Communities Research Articles

Sizing mudsnails: Applying superpixels to scale growth detection under ocean warming

Abstract The expansion of scientific image data holds great promise to quantify individuals, size distributions and traits. Computer vision tools are especially powerful to automate data mining of images and thus have been applied widely across studies in aquatic and terrestrial ecology. Yet marine benthic communities, especially infauna, remain understudied despite their dominance of marine biomass, biodiversity and playing critical roles in ecosystem functioning. Here, we disaggregated infauna from sediment cores taken throughout the spring transition (April–June) from a near‐natural mesocosm setup under experimental warming (Ambient, +1.5°C, +3.0°C). Numerically abundant mudsnails were imaged in batches under stereomicroscopy, from which we automatically counted and sized individuals using a superpixel‐based segmentation algorithm. Our segmentation approach was based on clustering superpixels, which naturally partition images by low‐level properties (e.g., colour, shape and edges) and allow instance‐based segmentation to extract all individuals from each image. We demonstrate high accuracy and precision for counting and sizing individuals, through a procedure that is robust to the number of individuals per image (5–65) and to size ranges spanning an order of magnitude (<750 μm to 7.4 mm). The segmentation routine provided at least a fivefold increase in efficiency compared with manual measurements. Scaling this approach to a larger dataset tallied >40k individuals and revealed overall growth in response to springtime warming. We illustrate that image processing and segmentation workflows can be built upon existing open‐access R packages, underlining the potential for wider adoption of computer vision tools among ecologists. The image‐based approach also generated reproducible data products that, alongside our scripts, we have made freely available. This work reinforces the need for next‐generation monitoring of benthic communities, especially infauna, which can display differential responses to average warming.

Habitat forming species explain taxonomic and functional diversities in a Mediterranean seamount

Complexity provided by habitat-forming species in marine ecosystems has been linked to higher species richness and biodiversity as well as enhancing ecosystem functioning. This study assesses how the presence of biogenic component of benthic habitats affects the taxonomic richness and functional diversities of a seamount benthos. We used a variety of complementary metrics on abundance data and quantitative community analyses to detail the composition, structure, diversity and functionality of eight biogenic and five non-biogenic benthic habitats across the Seco de los Olivos Seamount, located to the south of the Iberian Peninsula, in the western Mediterranean. This study shows that the presence of habitat-forming species in benthic habitats increases richness and enhances α and functional diversities. Their influence is more evident in soft and mixed bottoms, where the multiplying effect on structural complexity is proportionally greater than in rocky habitats. Biogenic habitats hosted a higher number of single species in comparison with non-biogenic habitats. The presence of habitat-forming species also determines β diversity among habitats at similar depth and type of substrate, with variation in species richness responsible for the most β diversity; turnover, however, dominated β diversity among habitats of different environments. Species richness hotspots were also associated to biogenic structures and were found restricted to the summit of the central guyot and other areas located on the surrounding ridges. Different functional composition of these benthic habitats also suggested differences in ecosystem functioning: biogenic habitats resembled more stable or at advanced stages of successional maturity than non-biogenic habitats and are characterized by biological traits that allow them to better promote benthic-pelagic coupling. From aconservation perspective an increased functional redundancy was found related to the occurrence of habitat-forming species in high abundance, which favours functional replacement and makes communities less vulnerable to environmental changes. The results of this study can help managers to develop specific management tools to ensure the future evaluation and monitoring of benthic communities.

Facultative scavenging feeding habits in Acanthurus chirurgus (Bloch, 1787) (Acanthuriformes: Acanthuridae).

The family Acanthuridae is a key component of coral reef ecosystems as it controls macroalgae biomass buildup. During routine monitoring of benthic communities in the Mexican Caribbean, we observed unusual behaviour of a group of Acanthurus chirurgus, which were feeding on a tuna head left on site by travel tour personnel. This phenomenon has been documented in other herbivorous fish species, especially in places where tourism is a major coastal activity. Although many Acanthurus seek additional sources of protein by feeding on detritus, it is unusual for them to feed directly on fish flesh. Acanthurus chirurgus will incorporate proteins from animal tissues whenever the opportunity arises. Such opportunities occurred rarely in the past, but have become more frequent recently, related to increasing tourism activities where flesh is used as bait to attract the surrounding fauna.

Assessment of the impact of salvaging the Costa Concordia wreck on the deep coralligenous habitats

The coralligenous habitats found in the Mediterranean Sea are hotspots comparable in biodiversity to tropical reefs. Coralligenous reefs are vulnerable to many human pressures, thus they are among the most threatened habitats in the Mediterranean Sea. In this study, we assessed the impacts on coralligenous habitats of activities associated with salvaging the wreck of the Costa Concordia cruise ship. After its partial foundering in 2012, the Costa Concordia remained adjacent to the eastern coast of Giglio Island (Tuscany, Italy), in the Tyrrhenian Sea, for over two years. Its salvage required high-impact engineering works, during the course of which monitoring of benthic communities was undertaken. We performed Rapid Visual Assessment (RVA) sampling (using recorded video) from 17 stations located between 35 and 76m depth and characterized by coralligenous habitats. Sampling activity was performed during the summers of 2012, 2013, and 2014. In parallel, chemical and physical water parameters were measured continuously from summer 2012 to the end of summer 2014, in order to detect any perturbation in natural conditions caused by salvage activities. We assessed the ecological quality of coralligenous habitats by applying the COARSE (COralligenous Assessment by ReefScape Estimate) index, based on the RVA approach. Slight modifications were applied to one of the descriptors of the COARSE index in order to adjust for study site features. There was clear evidence of a reduction in coralligenous habitats quality. Assemblages, slope, type of pressure, and distance from the source of disturbance played a pivotal role in characterizing bottom quality. The index was shown to have an easy and cost-effective application, even in waters deeper than its calibration specification; furthermore, the modification reported here may increase its potential applications.

Enhancing environmental performance during Wheatstone dredging through science and innovation

Dredging for the Chevron-operated Wheatstone LNG Project, near Onslow, Western Australia, involved movement of approximately 30 Mm3 of material over 23 months to provide safe navigation for LNG export as well as trunkline installation and stabilisation. Dredging was carried out in a sub-tropical, inshore environment near to biological benthic communities including corals, seagrasses, macroalgae and filter feeders, deemed sensitive to elevations in turbidity and/or sedimentation associated with dredging. Science and innovative technology was used to proactively and adaptively management dredging in order to afford a high level of environmental protection. Water quality data was transmitted via satellite to Perth where it was compared, daily, against management triggers derived from scientific analysis of an extensive dataset collected during a previous, nearby, dredging program. Accurate hindcast modelling, combined with MODIS satellite imagery, provided oversight of the extent and cause of observed turbid plumes, while forecast modelling provided predictions of the potential impacts of upcoming dredging activities, allowing for proactive changes to dredging activities to minimise potential impacts. Monitoring of benthic communities was undertaken using remotely operated underwater vehicles (ROVs) and water quality monitoring in the latter part of the program was undertaken using remotely operated Wave Gliders (Liquid Robotics), both of which resulted in significant safety improvements and cost savings and over traditional monitoring methods. Post-dredging surveys of benthic communities indicated that, despite their proximity to dredging activities and the enormity of dredged volumes, no detectable impacts had occurred as a result of dredging.

Early detection of potentially invasive invertebrate species in Mytilus galloprovincialis Lamarck, 1819 dominated communities in harbours

Constanţa harbour is a major port on the western coast of the semi-enclosed Black Sea. Its brackish waters and low species richness make it vulnerable to invasions. The intensive maritime traffic through Constanţa harbour facilitates the arrival of alien species. We investigated the species composition of the mussel beds on vertical artificial concrete substrate inside the harbour. We selected this habitat for study because it is frequently affected by fluctuating levels of temperature, salinity and dissolved oxygen, and by accidental pollution episodes. The shallow communities inhabiting it are thus unstable and often restructured, prone to accept alien species. Monthly samples were collected from three locations from the upper layer of hard artificial substrata (maximum depth 2 m) during two consecutive years. Ten alien macro-invertebrate species were inventoried, representing 13.5% of the total number of species. Two of these alien species were sampled starting the end of summer 2010, following a period of high temperatures that triggered hypoxia, causing mass mortalities of benthic organisms. Based on the species accumulation curve, we estimated that we have detected all benthic alien species on artificial substrate from Constanţa harbour, but additional effort is required to detect all the native species. Our results suggest that monitoring of benthic communities at small depths in harbours is a simple and useful tool in early detection of potentially invasive alien species. The selected habitat is easily accessible, the method is low-cost, and the samples represent reliable indicators of alien species establishment.