Manuel M. González-Duarte

Benthic assemblages, biodiversity and invasiveness in marinas and commercial harbours: an investigation using a bioindicator group.

Abstract Fouling communities on artificial marine structures are generally different from benthic communities in natural rocky habitats. However, they may also differ among different types of artificial structures. Two artificial structures in direct contact with arriving vessels were compared: floating pontoons within recreational marinas, and sea-walls within commercial harbours. Natural rocky habitats were used as a reference, and the genus Eudendrium (Cnidaria, Hydrozoa) was chosen as a bioindicator. The assemblages were different among the three types of habitat studied, with different species characterising each habitat. The probability of finding an invasive Eudendrium species was significantly higher on pontoons. Diversity was the lowest on pontoons, but it was not significantly different between sea-walls and natural rocks. In general, a barrier to the spread of exotic species exists between harbours and natural rocky habitats. Floating pontoons seem to be a less suitable habitat for native fauna and a key element in marine biological invasions.

Diet of common dolphinfish (Coryphaena hippurus) in the Pacific coast of Ecuador

The diet and the feeding habits of the common dolphinfish ( Coryphaena hippurus ) in the Pacific coast of Ecuador was assessed by examining 320 stomachs of individuals ranging from 51 to 149 cm in total length. Fish was the predominant prey group in the diet (Alimentary Index, %AI = 95.39) followed by cephalopods (%AI = 4.13) and crustaceans (%AI = 0.48). Among the 17 prey items that make up the dolphinfish diet, the Exocoetidae family was the most important prey (%AI = 57.13), Dosidicus gigas being the most abundant invertebrate species (%AI = 7.65). Feeding patterns were evaluated using the graphing method of Amundsen, which suggested that this species shows a varying degree of specialization on different prey taxa. Thus, while some species were unimportant and rare ( Hippocampus hippocampus, Lagocephalus lagocephalus , Gobiidae and Argonauta sp.), several dolphinfishes showed a high degree of specialization on Scombridae, Pleuroncodes planipes, Portunus xantusii and Opisthonema libertate . Size-related and temporal shifts in dietary composition were investigated by PERMANOVA analysis, which showed wide variations among size classes and periods of capture. The results of this study indicate that the common dolphinfish is an opportunistic feeder, which is capable of consuming a wide variety of schooling epipelagic organisms.

Cnidarian Alien Species in Expansion

The study of the diversity and composition of marine communities is the first step in understanding the development of marine ecosystems. While some cnidarian populations are in decline, others invade new regions and habitats. The pressure of the human actions on the marine ecosystems has increased in the past decades. The artificial structures in marine environments, shipping, aquaculture, global warming and interoceanic canals have contributed to the dispersion, establishment and invasion of many places by alien species around the world, in some cases, with major ecological and socio-economic impacts. Some cnidarian species may serve as examples of the truly widespread reach of invasive species. Benthic phase of hydroids and anthozoans are common components of harbours and fouling communities and, probably, they have been transported on ship hulls. Ephyrae and hydromedusae are also frequently found in ballast water. Additionally, the global climatic change allows cnidarian of tropical affinity to extend their range into the temperate zones. The biological invasions and range extensions may cause local native biodiversity and economic losses. Only recently have these biological invasions attracted the attention of the scientific community. Though invasive alien cnidarians are recognized now as a global threat to biodiversity, and monitoring their presence and impacts is considered a prerequisite for marine environmental management and sustainable development, it seldom takes place even in the coastal regions most vulnerable to introductions

Study of the influence of physical, chemical and biological conditions that influence the deterioration and protection of Underwater Cultural Heritage

Two wrecks related to the Battle of Trafalgar (1805) were studied. Following the guidelines of the UNESCO-2001 Convention for the Protection of the Underwater Cultural Heritage, a holistic and interdisciplinary approach based on the development of four of the thirty-six Rules of this international agreement was applied. A non-destructive survey technique was developed to obtain information from the scattered cannons and anchors without altering their condition (Rule 4). The work performed provided information about the origin of both wrecks, the Fougueux and the Bucentaure, two ships of the line of the French Navy, and allowed to characterize the state of conservation at each site without jeopardizing their future conservation in the marine environment. In addition, measurements of the main physical, chemical and biological variables allowed correlating the conservation status at each site with the marine environmental conditions (Rule 15). Thus, in Fougueux shipwreck large iron objects are corroding at a higher rate (between 0.180 and 0.246mmpy) due to high sediment remobilization and transport induced by waves at this site, causing damage by direct mechanical effect on metallic material and by removing the layer of corrosion products developed on the artefacts. Meanwhile artillery on Bucentaure site, covered with thick layers of biological concretion, is well preserved, with lower corrosion rates (0.073 to 0.126mmpy), and archaeological information is guaranteed. Finally, the effectiveness of the cathodic protection as a temporary measure for in situ conservation (Rule 1) was evaluated on a cannon. The use of a sacrificial anode after 9months reduced the average corrosion rate (from 0.103 to 0.064mmpy) and the percent of corrosion rate in 37.9%. These results are very useful for developing a decision making system of the Site Management Program, based on predictive models of artefacts permanence and risk factors in the marine environment (Rule 25).