Improving Scientific Knowledge of Mallorca Channel Seamounts (Western Mediterranean) within the Framework of Natura 2000 Network

The scientific exploration of Mallorca Channel seamounts (western Mediterranean) is improving the knowledge of the Ses Olives (SO), Ausias March (AM), and Emile Baudot (EB) seamounts for their inclusion in the Natura 2000 network. The aims are to map and characterize benthic species and habitats by means of a geological and biological multidisciplinary approach: high-resolution acoustics, sediment and rock dredges, beam trawl, bottom trawl, and underwater imagery. Among the seamounts, 15 different morphological features were differentiated, highlighting the presence of 4000 pockmarks, which are seafloor rounded depressions indicators of focused fluid flow escapes, usually gas and/or water, from beneath the seabed sediments. So far, a total of 547 species or taxa have been inventoried, with sponges, fishes, mollusks, and crustaceans the most diverse groups including new taxa and new geographical records. Up to 29 categories of benthic habitats have been found, highlighting those included in the Habitats Directive: maërl beds on the summits of AM and EB, pockmarks around the seamounts and coral reefs in their rocky escarpments as well as fields of Isidella elongata on sedimentary bathyal bottoms. Trawling is the main demersal fishery developed around SO and AM, which are targeted to deep water crustaceans: Parapenaeus longirostris, Nephrops norvegicus, and Aristeus antennatus. This study provides scientific information for the proposal of the Mallorca Channel seamounts as a Site of Community Importance and for its final declaration as a Special Area of Conservation.

Marine invertebrates associated with rhodoliths/maërl beds from northeast Brazil (State of Paraíba)

This study investigates the marine macroinvertebrate fauna of rhodolith beds (non-geniculated red corallinaceaous algae) in northeast Brazilian. A total of 57 species were identified, belonging to six phyla (Platyhelminthes, Annelida, Sipuncula, Mollusca, Arthropoda and Echinodermata), of which 50 are considered here as new records for the Paraíba State. Annelids (Class Polychaeta) were the most representative taxa in Miramar and Seixas Beaches, while molluscs were dominant in Maceió Beach. This is the first study that includes an identification key, diagnostic features and distribution patterns worldwide and local (including new records) of the marine invertebrate fauna associated with rhodolith beds in northeast Brazil (State of Paraíba). Sampling events were performed in 2018, at low tide in the intertidal to shallow subtidal zones (1.5 and 4.0 m depth), in Miramar, Seixas and Maceió Beaches. A total of 17 species were found for the first time on Seixas Beach, as well as all identified species for Miramar and Maceió. This study tries to contribute to the knowledge of marine invertebrates in northeast Brazilian shallow habitats, providing a baseline for future environmental studies.

Declining maerl vitality and habitat complexity across a dredging gradient: Insights from in situ sediment profile imagery (SPI)

Maerl beds form complex biogenic benthic habitats, characterized by high productivity as well as diverse biological communities. Disturbances associated with extraction and/or fishing activities using mobile bottom-contacting gears such as clam-dredges induce the most severe and long-term effects on these fragile habitats. We here investigated the effects of dredge-fishing on maerl in the bay of Brest (France). We quantified maerl beds structure and vitality across a fine scale quantified dredging intensity gradient through the acquisition of in-situ images of beds cross-section using Sediment Profile Imaging system (SPI). Declines in the proxies of maerl vitality and habitat complexity were measured across the gradient, and were associated with significant changes in the vertical distribution of live and dead maerl as well as of interstitial space. Fishing with dredges caused maerl mortality, substratum compaction, and decreasing habitat complexity. SPI imaging techniques also allowed for an assessment of changes in spatial heterogeneity that dredging created on several aspects of the structure and vitality of maerl beds. It suggests that direct and indirect disturbances induced by dredging are not acting at the same spatial scale, and can thereby differentially affect the ecosystem functions linked to vitality and habitat complexity.

Morphological variability of Jania longifurca (Corallinales, Rhodophyta) in Galicia, northwestern Spain

Material of Jania J.V.Lamour. with a different morphology from the typical one attributed to J. longifurca Zanardini and J. rubens (L.) J.V.Lamour.—the only species in this habitat in Galicia—has been detected in the maerl beds of Galicia. This morphology consists on: thin intergenicula, an irregular pattern of dichotomies and secondary attachment discs that facilitate the refixation to the substrate, all of them similar to those of other southern species of Jania. Nevertheless, the integrative taxonomic study of this material and other collections from rocky habitat confirmed its identification as J. longifurca. Thereby, the atypical morphology with thin intergenicula and secondary attachment disc is dominant in samples of J. longifurca from maerl beds, while the samples from rocky environments showed the typical robust intergenicula. Moreover, molecular analysis resolved some phylogenetic affinities with samples from New Zealand, where this species is not recorded. It is concluded therefore the morphological variation related to the environment and it is evident the need of molecular studies to clarify this genus taxonomy, which is based fundamentally on morphological characters.

Shading by invasive seaweeds reduces photosynthesis of maerl from the Ría de Vigo (NW Spain)

The overgrowth and shading of several alien species along the European Atlantic coast are expected to reduce photosynthesis of maerl, decreasing its growth and fitness. In this work, three shade levels (0, 20 and 50%) were set up under laboratory conditions to simulate different competitive scenarios potentially affecting maerl beds. Live individuals ofSargassum muticumandUndaria pinnatifidawere placed over maerl cultures, and the effects of shading were assessed by chlorophyllafluorescence using a pulse-modulated fluorescence monitoring system. Photosystem II efficiency was measured as the ratio of variable to maximal fluorescence (Fv/Fm) as a proxy for the stress experienced by maerl. According to our data, irradiance reduction results in a small, yet significant, impact on the PSII efficiency of maerl, which could have fitness consequences.