Gonçalves, J.M.S.; Monteiro, P., Afonso, C., Oliveira, F., Rangel, M., Machado, M., Veiga, P., Leite, L., Sousa, I., Bentes, L., Fonseca, L. & Erzini, K. (2007). Cartography and characterization of the marine communities off the National Underwater Ecological Reserve between the Arade river and Ponta da Piedade. (in portuguese). Final report. ARH Algarve. Universidade do Algarve, CCMAR, Faro, 122 pp + annexes.

RENSUB IV: Cartography and characterization of the marine communities off the National Underwater Ecological Reserve between the Arade river and Ponta da Piedade.

Abstract

The Algarve coast, presents a significant portion of territory that is part of the designated National Nature Reserve, in its underwater slope (0 to 30m depth - RENSUB), especially when compared with the equivalent on land. The digital mapping of all habitats and subtidal marine communities of the Algarve coast will contribute to the definition of criteria for the establishment of special areas of marine protection, potentially contributing to the establishment of a National Network of Marine Protected Areas and the implementation of Natura 2000 in the marine environment. It will also help facilitate and sustain the processes of management, licensing, supervision and monitoring of activities related to the marine environment (e.g., dredging, aquaculture and wind farms offshore) promoting decision-making concerning the use of these maritime and coastal environments based on criteria of accuracy and fairness.

By dealing with the mapping of marine biodiversity in the Algarve, this project is framed in the main directives of the National Strategy for Nature Conservation and Biodiversity and the National Strategy for the Ocean, including the promotion of scientific research and knowledge of the natural heritage, species monitoring, habitats and ecosystems; the establishment of the Nature Conservation Network Foundation, the National System for Hazardous Areas and spatial ordering and planning of oceanic and coastal areas, protecting fully the valuable natural marine heritage of Portugal. It is also in line with the main European Directives and other international bodies to which the Portuguese Government is committed: EU Habitats Directive, Natura 2000 Extension of the marine environment, the EU Water Framework Directive, EU Framework Directive “Marine Strategy”, European Maritime Policy, Common Fisheries Policy, the Convention for the Conservation of Biodiversity (CBD), Agenda 21, ICES and OSPAR Convention.

The present study is a continuation and extension of the RENSUB I, II and III projects (Gonçalves et al., 2004b, 2007b, 2008b), to the surveying and mapping of the main coastal biotopes (habitats and species) of the Central Algarve region. More specifically, we sought to map the communities of seaweeds and marine plants, benthic macroinvertebrates and fish in the underwater section of coastline from 0 to 30 m depth, between the mouth of the Arade River (Portimão) and Ponta da Piedade (Lagos).

To achieve these objectives, a detailed study of the seabed was carried out from May 2009 to June 2010, based on seabed geological maps (granulometry, type of bottom) from the tests conducted by the ARH/CCDRAlgarve. The samples had a seasonal character and in total involved 62 days at sea. Of these, 45 days corresponded to 190 individual scuba dives (about 9500 minutes of scuba diving, 22 sampling points) and the remaining 17 days at sea to a total of 152 beam trawls (100700 m2, 38 sampling points).

A stratified random sampling plan by depth and bottom type was carried out using three main underwater sampling methods: underwater visual census (transects) for benthic macroinvertebrates and fish fauna found in rocky substrates; quadrat method to estimate the percentage of vegetation cover of bedrock and beam trawl for benthic macroinvertebrates and fish fauna of mobile substrates (fine sand/medium and coarse).

Multivariate analyses were used for the basic data processing and geostatistics and generalized additive and linear models (GLM and GAM) to map multiple variables (diversity, density) and indicators designed for this purpose, as the index of ecological importance.

The study and mapping of the seabed from 0 to 30 meters depth between the mouth of the Arade River (Portimão) and Ponta da Piedade (Lagos) were able to identify a total of 567 species, consisting of 116 fish (17.5%), 461 (76.1%) benthic macroinvertebrate and 39 algae (6.4%) species, adding 48 new species to previous phases of this study (RENSUB I, II and III). In total, for all of these studies, approximately 1495 species (1349 animals + 146 algae/plants) were recorded, increasing what is already the largest inventory of marine species of the Algarve coast and one of the largest nationally.

At this stage, the sampling effort allowed the discovery of three new species recorded for the first time in Portugal: a white anemone Parazoanthus anguicomus (Norman, 1868) whose presence in the Algarve is currently its southern limit of its distribution; a colonial hydrozoan Sertularella crassicaulis (Heller, 1868), first record for the Atlantic coast of continental Europe and a box crab Calappa cf. tuerkayana Pastore, 1995, which will be the first record for the Atlantic coast of continental Europe when the species identity is confirmed.

Taking into account the previous projects (Gonçalves et al., 2004a, 2004b, 2007b, 2008b), the global inventory of new recorded species for Portugal has reached a total of 36, one of which is new to science and three that are still under proper study as new species, demonstrating the importance and necessity of such works for understanding of marine biodiversity, with the aim of contributing to conservation measurements in the near future. The inventory of marine biodiversity contains 227 species that have commercial value, which will be 447 species if we consider all phases of RENSUB. From this set of species with commercial interest, 161 are of ornamental interest (aquarium, collecting, decorating) and 46 have components used in the production of biomedical products and/or are used in laboratory experimentation.

In this context, this project was the basis for launching the project “Exploitation of the bacterial diversity contained in marine sponge metagenomic” currently taking place and that will measure and determine the importance of living microorganisms associated with sponges of the genus Spongia, and Sarcotragus and Ircinia in particular in the production of metabolites potentially useful for the pharmaceutical industry.

Following the classification of the ICN (1993), 20 of the recorded species were “commercially threatened”, 6 species “insufficiently known” and another two are of “Undetermined” status. Finally, 16 species are listed in the Berne Convention and 6 in the Red List of the International Union for Conservation of Nature (IUCN, 2010). In general, there was a clear distinction between mobile substrates or “sand” and the hard or “rocky” substrates. Rocky substrates were clearly characterized by a larger biodiversity and in particular a higher density of organisms than the mobile substrates. The structuring species of these bedrock habitats are brown algae Dictyota dichotoma and Halopteris filicina, red algae Asparagopsis armata, Gelidium latifolium and Peyssonnelia rubra, calcareous or limestone algae Lithophylum incrustans, L. expansum and Mesophyllum lichenoides, anemones Anemonia sulcata, Aiptasia diaphana and Parazoanthus axinellae, bryozoans or false corals Myriapora truncata, sea urchin Paracentrotus lividus, gastropod top shells Bolma rugosa and Gibbula cineraria, sponges Phorbas fictitius and Axinella polypoides, sea cucumber Holothuria mammata and gorgonians Eunicella labiata and Leptogorgia sarmentosa.

The rocky bottoms were considered an essential habitat for many marine fish such as juveniles and adults of benthic and cryptic species like gobies Gobius xanthocephalus and Parablennius pilicornis, species of rockfish, demersal species such as Ctenolabrus rupestris as well as the Mediterranean rainbow wrasse Coris julis and commercially valuable fish Diplodus vulgaris, locally known as "Safia" (Two-banded seabream).

Sandy bottoms were dominated by flat fish (e.g., Buglossidium luteum, Arnoglossus thori, Serranus hepatus and Microchirus boscanion), manly belonging to the Families Soleidae and Bothidae, a group of species well adapted to soft bottoms where they live, feed and reproduce. The strong concentration of a single species, Buglossidium luteum, might be associated with high abundance of this species in the Arade estuary, which might influence the structure of the surrounding sandy bottom benthic communities. The dominance of flatfish in mobile substrate suggests that they will act as top predators, rather than what was found in other sandy areas adjacent to Albufeira and Faro, where this status belongs to echinoderms.

In terms of key species for monitoring purposes, the most relevant would be Anemonia sulcata and Diplodus vulgaris for rocky substrates and Buglossidium luteum, Arnoglossus thori and Ophiura texturata for sandy bottoms. This monitoring could be done by video transects and/or beam trawl in the sandy substrates and by visual census surveys for rocky or submerged rock bottoms. Both in sandy and rocky substrates, the seasonal conditions clearly influence density and diversity. These differences become particularly evident between extreme seasons, winter-spring in sandy bottoms and in winter-summer for rocky bottoms. This seasonality will reflect the relationships established between the temperature and hydrodynamics and different life cycles of many benthic species. As in previous studies, the differences between the variety of rocky bottoms studied were determined by the depth and nature, topography and hydrodynamics prevailing in each area while in the mobile substrates significant differences were only observed among communities of two extreme depth strata (0-10 vs. 20-30), with an increased diversity and abundance with depth. The absence of towed fishing gears (e.g., ganchorra - bivalves dredge), the presence of high habitat complexity, greater hydrodynamic stability and stable environmental parameters (e.g., temperature, salinity, turbidity, dissolved oxygen and organic composition) may be the cause for a higher biological richness at greater depths.

The communities typically found in both substrates (sandy and rocky) did not differ much from the communities of fauna described from the previously mapped adjacent areas (RENSUB III), although in the case of the mobile substrate there were some differences found in gravel sand bottoms between Albufeira and Faro (RENSUB I and II), which might be related to different particle sizes, much finer to the West and mostly influenced by the contributions of various freshwaters streams, with emphasis on the Arade estuary. The continuity of these communities was expected because of the short biogeographical extension and the fact that most species identified have a wide geographic distribution, being common both in the Mediterranean as well as in the nearby Atlantic Ocean. This study thereby enabled us to enhance the basic conclusions obtained in previous studies of the Central Algarve National Underwater ecological reserve - RENSUB (Gonçalves et al., 2004b, 2007b, 2008b).

The classification of various biotopes followed once more the general rules determined by the European Nature Information System (EUNIS, Davies et al., 2001) and the UK Joint Nature Conservation Committee (JNCC, Connor et al., 2004) which show the dominant species and a set of conspicuous species as well as characteristics of certain environmental conditions and/or a particular biotic habitat. The method of discrimination of biotopes, however, was original, and following the previous study (RENSUB III), consisted of four steps that go through the recovery of species composition, frequency of occurrence, abundance and rarity. However, in the present study, a novel method of ecological zonation of the marine environment was introduced in which the infralittoral and circalittoral zones are separated in quantitative terms based on algal cover.

In general terms, and according to the new methodology, several important biotopes stand out in the study area: subtidal coastal rocky substrate (EUNIS A3.24A), deep subtidal (EUNIS A3.24B), coastal circalittoral (EUNIS A4.28) and two biotopes of mobile subtidal substrate (EUNIS A5.23) and circalittoral (EUNIS A3.25). It is important to state that the rocky biotope associated to circalittoral EUNIS classification does not exist, so it is an original proposal of this study.

To determine the richest areas in terms of marine biodiversity, the same patterns used in previous phases of the project RENSUB (Gonçalves et al., 2004b, 2007b, 2008b) were followed, integrating elements of density and biological diversity (indexes of Margalef and Shannon) and relative abundance and distribution of species with conservation value. The iterative weighting of the variables mentioned, again followed the Delphi approach, with expert consultation on coastal ecology and continued appraisal, albeit indirectly, of the areas considered as nurseries for juveniles of commercial species and the spawning areas.

The base support of the theoretical model dealing with the Index of Ecological Importance (IIE) resides in the components of viability and threat, vulnerability and rarity and representativeness. It´s benefits remain focused on flexibility and capability to be adjusted and updated, providing a Geographic Information System platform, a suitable tool for a spatial management of the marine environment. Taking this model in consideration, the priority areas in terms of biodiversity conservation are associated with the subtidal massif rock of the Bay of Lagos (10-20m), rocky substrate of the deep subtidal.