Alan Deidun

Low faunal diversity on Maltese sandy beaches: fact or artefact?

Eight sandy beaches on Malta and two on Gozo were sampled for macrofauna to test the hypothesis that Maltese beaches have an intrinsically low diversity. Stations distributed in the supralittoral (dry zone), mediolittoral (wet zone) and upper infralittoral (submerged zone to 1 m water depth) were sampled by sieving core samples and standardised searching during daytime, and pitfall trapping and standardised sweeping of the water column using a hand-net at night, as appropriate. Physical parameters of the sediment were measured and human occupancy of the beaches was estimated. From the supralittoral and mediolittoral, 39 species represented by 1584 individuals were collected by the combined techniques of pitfall trapping, sieving and standard searching. For Ramla beach, which had the highest diversity, 267 individuals representing 25 infaunal species were collected by sieving from a combined volume of 1.175 m 3 of sand, and 149 individuals representing 28 epifaunal species were collected by standardised searching from a combined area of 700 m 2 of sand during two winter and two summer sampling sessions between 1992 and 1993. For nine other beaches sampled during the summer of 2000, only six macrofaunal species were collected from core samples, with overall population densities ranging from 4.13 to 45.45 individuals m � 2 . Only 92 individuals belonging to 12 species were collected by hand-net from the uppermost infralittoral of five beaches sampled using this method during the summer of 2000. Taxa of gastropods, bivalves, decapods, mysids and staphylinid beetles generally abundant on Mediterranean sandy beaches, were entirely absent from the beaches sampled. Few correlations that could explain the impoverishment of Maltese sandy beaches were found between physical parameters and faunal abundances, and other factors such as inadequate sampling effort, human disturbance and marine pollution were also excluded; however, seasonally biased sampling may partly explain the results obtained. One factor that may explain why certain species are missing could be lack of recruitment, due to Malta’s geographical isolation from the European and African mainlands. 2003 Elsevier Ltd. All rights reserved.

Rocky Shore Biotic Assemblages of the Maltese Islands (Central Mediterranean): A Conservation Perspective

Abstract Limestone rocky shores constitute ca 90.5% of the 272km coastline of the Maltese islands. Only some 40% of this rocky coastline is gently sloping and easily accessible. Such shores are heavily impacted with 96% of the accessible coastline dominated by tourist-related or by maritime activities. We characterised the biotic assemblages of lowland Maltese rocky shores and tested the popularly held view that given the scarce variation in physical characteristics, such shores form a homogenous habitat. Belt transects were laid perpendicular to the shoreline from biological zero to the adlittoral zone on seven Coralline Limestone and one Globigerina Limestone shores. Cover (for algae and encrusting species) or population density (for animals except sponges) were estimated using 0.5m X 0.05m quadrats placed contiguously for the first few metres and then at regularly spaced intervals. Overall, 19 faunal and 47 floral species, and 10 faunal and 8 floral species were recorded from the Coralline and Globigerina transects respectively, with 60.8% faunal and 25.6% floral species common to the two substrata. Hierarchical clustering showed that the Coralline and Globigerina transects harboured distinct biotic assemblages and identified an upper shore assemblage dominated by the littorinid Melarhaphe neritoides and barnacles, and a lower shore assemblage dominated by algae and molluscs; a mid-shore transition zone where certain species from both assemblages reached peaks of abundance was present in almost all Coralline and the majority of Globigerina transects. Differences in biota between the two types of shore are most likely primarily related to differences in microtopography and, to a lesser degree, to exposure. It is concluded that in spite of gross physical similarity, Maltese lowland rocky shores are biotically inhomogeneous, making conservation of individual sites much more important than previously thought.

First record of Cassiopea andromeda (Scyphozoa: Rhizostomeae: Cassiopeidae) from the central Mediterranean Sea

The occurrence of the scyphozoan Cassiopea andromeda is reported from the Maltese Islands, where a sizable aggregation was found in Marsamxett Harbour. This is the first record of this circumtropical species from the central Mediterranean Sea, hitherto known from the Levantine and Aegean basins. It is suggested that the most likely vector responsible for transporting this species to the Maltese Islands is shipping.

Environmental quality assessment of Grand Harbour (Valletta, Maltese Islands): a case study of a busy harbour in the Central Mediterranean Sea

Contamination levels by plastic debris, trace elements and persistent organic pollutants were assessed and related to macrobenthic diversity within soft bottoms of Grand Harbour (Malta, Central Mediterranean). Sediment toxicity was evaluated by ecotoxicological method, deploying Bacteria (Vibrio fischeri), Echinodermata (Paracentrotus lividus) and Crustacea (Corophium orientale). Univariate analysis (Pearson’s test) was used to test relationships between biodiversity indices, pollutants and grain size. A multivariate approach (PERMANOVA) was applied to investigate for any significant differences among sampling stations concerning plastic abundances and to test the relationship between infaunal abundances and pollutant concentrations (the BIOENV test). Significant differences in the plastic abundances were found between sampling stations. The lowest value for Shannon-Wiener biodiversity index was associated to the highest sediment pollution level. Multivariate analyses suggest that MBT and TBT were factors that most influenced macrozoobenthic abundance and biodiversity. The bivalve Corbula gibba and the introduced polychaete Monticellina dorsobranchialis were the most abundant found species

First characterisation of a Leiopathes glaberrima (Cnidaria: Anthozoa: Antipatharia) forest in Maltese exploited fishing grounds

Abstract A remotely operated vehicle (ROV) survey conducted in the deep (250–400 m) Maltese waters in 2013 revealed, for the first time, the characteristics of an extended coral forest, constituted almost exclusively by the arborescent, longevous black coral Leiopathes glaberrima. This species is a major component of the deep coral forests of the Mediterranean Sea and its occurrence in dense populations greatly enhances the benthic biodiversity of the sites in question. The existence of such a complex benthic ecosystem is particularly interesting for Malta, since this area represented, in the 1980s, the only sanctioned site within the Mediterranean basin for the commercial exploitation of black corals. The occurrence of the large black coral population hints that, at least within the investigated area, the coral resource has not greatly suffered from past coral harvesting activities. The major current concern, however, is represented by the massive anthropogenic impact due to benthic fishing activities carried out on the rocky bank, as evidenced by the high amount of discarded fishing gear directly impacting the specimens. The data here presented, despite being preliminary in nature, suggests that the investigated benthic area should be considered a vulnerable marine ecosystem valuable for future scientific monitoring exercises. Appropriate benthic fishing restrictions for the area in question, which might be considered for inclusion within an marine protected area (MPA), should be contemplated.

Distribution of resting cysts of the potentially toxic dinoflagellate Alexandrium pseudogonyaulax in recently-deposited sediment within Bizerte lagoon (Mediterranean coast, Tunisia).

This study investigated the spatial distribution of Alexandrium pseudogonyaulax resting cysts in recently-deposited sediment of Bizerte lagoon (South-Western Mediterranean, Tunisia). This lagoon is the subject of many anthropogenic impacts, such as holding important fishing and aquaculture activities. A. pseudogonyaulax has been shown to produce Goniodomin A, which is a biologically-active compound. We showed that this dinoflagellate produces two types of resting cysts, which could be distinguished by the presence or the absence of a paratabulate wall. The average cyst density across the whole lagoon was rather high, reaching 639 cysts g(-1) of dry sediment (DS). Cyst densities varied widely among the sampled stations, with the highest density of 1685 cyst g(-1)DS being recorded at station 51 near a mussel farm. With respect to sediment characteristics, the highest cyst densities were found within silty sediments with high water content values. The distribution of A. pseudongoyaulax cysts in Bizerte lagoon appears to be related to hydrodynamic factors.

Mitochondrial DNA and microsatellites reveal significant divergence in the beachflea Orchestia montagui (Talitridae: Amphipoda)

Talitrids are semiterrestrial crustacean amphipods inhabiting sandy and rocky beaches; they generally show limited active dispersal over long distances. In this study we assessed levels of population genetic structure and variability in the talitrid amphipod Orchestia montagui, a species strictly associated to stranded decaying heaps of the seagrass Posidonia oceanica. The study is based on six populations (153 individuals) and covers five basins of the Mediterranean Sea (Tyrrhenian, Ionian, Adriatic, Western and Eastern basins). Samples were screened for polymorphisms at a fragment of the mitochondrial DNA (mtDNA) coding for the cytochrome oxidase subunit I gene (COI; 571 base pairs) and at eight microsatellite loci. MtDNA revealed a relatively homogeneous haplogroup, which clustered together the populations from the Western, Tyrrhenian and Eastern basins, but not the populations from the Adriatic and Ionian ones; microsatellites detected two clusters, one including the Adriatic and Ionian populations, the second grouping all the others. We found a weak geographic pattern in the genetic structuring of the species, with a lack of isolation by distance at either class of markers. Results are discussed in terms of probability of passive dispersal over long distances through heaps of seagrass.

Late quaternary coastal landscape morphology and evolution of the Maltese Islands (Mediterranean Sea) reconstructed from high-resolution seafloor data

Abstract The current strong motivation to explore those traces of the archaeological and prehistoric human heritage that presently lie submerged on the continental shelf requires large-scale and precise underwater mapping. One Mediterranean sector deserving particular attention is the Sicily Channel, which is critical for a better understanding of the Africa–Europe migratory routes and early civilization patterns due to its large expanses of shallow seabed that were partially or totally exposed at times of lower relative sea levels. We have focused our attention on the submerged continental margin of the Maltese archipelago. A detailed bathymetric map is here presented, and is discussed in terms of features interpretable as former subaerial landforms and inundated by sea-level rise following the Last Glacial Maximum lowstand at approximately –130 m. Our datasets combine multibeam surveys, Light Detection And Ranging (LiDAR)-derived digital terrain models (DTMs), Chirp sub-bottom profiler records and bottom samples acquired between 2009 and 2012. The main features identified are former river incisions, alluvial plains, karst landscapes (sinkholes, limestone plateaus), slide deposits and palaeoshorelines. This study provides a detailed topographical reconstruction of the palaeolandscape of this key region that is relevant to any future archaeological exploration of the Maltese offshore area.

Making the case for marine spatial planning in the Maltese Islands

Marine spatial planning (MSP) has been gaining in stature recently as an ecosystem-based tool for the management of marine space that promotes the sustainable and optimal use of resources with minimal stakeholder conflicts. Malta is the quintessential maritime nation, with a disproportionately large marine area compared to its terrestrial area. Nonetheless, its limited coastline, a considerable portion of which is inaccessible, poses inevitable conflicts between multiple marine activities and designations, including aquaculture, fishing, bunkering, coastal tourism, navigation, renewable energy installations, conservation of biological diversity and protected areas (on ecological criteria). This article makes the case to implement MSP-based policies and an applicable legal framework in the Maltese Islands.

A massive update of non-indigenous species records in Mediterranean marinas

The Mediterranean Sea is home to over 2/3 of the world’s charter boat traffic and hosts an estimated 1.5 million recreational boats. Studies elsewhere have demonstrated marinas as important hubs for the stepping-stone transfer of non-indigenous species (NIS), but these unique anthropogenic, and typically artificial habitats have largely gone overlooked in the Mediterranean as sources of NIS hot-spots. From April 2015 to November 2016, 34 marinas were sampled across the following Mediterranean countries: Spain, France, Italy, Malta, Greece, Turkey and Cyprus to investigate the NIS presence and richness in the specialized hard substrate material of these marina habitats. All macroinvertebrate taxa were collected and identified. Additionally, fouling samples were collected from approximately 600 boat-hulls from 25 of these marinas to determine if boats host diverse NIS not present in the marina. Here, we present data revealing that Mediterranean marinas indeed act as major hubs for the transfer of marine NIS, and we also provide evidence that recreational boats act as effective vectors of spread. From this wide-ranging geographical study, we report here numerous new NIS records at the basin, subregional, country and locality level. At the basin level, we report three NIS new to the Mediterranean Sea (Achelia sawayai sensu lato, Aorides longimerus, Cymodoce aff. fuscina), and the re-appearance of two NIS previously known but currently considered extinct in the Mediterranean (Bemlos leptocheirus, Saccostrea glomerata). We also compellingly update the distributions of many NIS in the Mediterranean Sea showing some recent spreading; we provide details for 11 new subregional records for NIS (Watersipora arcuata, Hydroides brachyacantha sensu lato and Saccostrea glomerata now present in the Western Mediterranean; Symplegma brakenhielmi, Stenothoe georgiana, Spirobranchus tertaceros sensu lato, Dendostrea folium sensu lato and Parasmittina egyptiaca now present in the Central Mediterranean, and W. arcuata, Bemlos leptocheirus and Dyspanopeus sayi in the Eastern Mediterranean). We also report 51 new NIS country records from recreational marinas: 12 for Malta, 10 for Cyprus, nine for Greece, six for Spain and France, five for Turkey and three for Italy, representing 32 species. Finally, we report 20 new NIS records (representing 17 species) found on recreational boat-hulls (mobile habitats), not yet found in the same marina, or in most cases, even the country. For each new NIS record, their native origin and global and Mediterranean distributions are provided, along with details of the new record. Additionally, taxonomic characters used for identification and photos of the specimens are also provided. These new NIS records should now be added to the relevant NIS databases compiled by several entities. Records of uncertain identity are also discussed, to assess the probability of valid non-indigenous status.