Filipe Rodrigues

TUNIPEX S.A. · Live Fish

Introduction Aquaculture practices, like any other human activity, affect the environment in different ways. Some can be considered beneficial while others are in conflict with long-term sustainability of natural ecosystems. Recently, some attention has been dedicated to the effects of discharges of effluents from certain types of aquaculture. Aquaculture operations cause the release of metabolic waste products such as faeces, pseudofaeces, excreta and uneaten food which is considered one of the most important factors causing organic and inorganic loading in the vicinities of aquatic farms (Grigorakis & Rigos, 2011). The amount of uneaten feed relies mostly on the personnel experience and qualifications, feeding management (automatic or hand feeding), and the ingredients comprising the feed (Grigorakis & Rigos, 2011; Pillay, 2004). Indeed, effluents from shrimp aquaculture typically are enriched in suspended solids, nutrients, chlorophyll a and with an increased biochemical oxygen demand (Páez-Osuna, 2001). Suspended solids have been considered one of the most important waste products affecting the quality of the receiving waters and their environment (Pillay, 2004). Aquatic animals need a high concentration of protein in their feed since their energy production pathway requires the oxidation and catabolism of proteins. Estimates of nutrient retention and potential release by fish into the water are not readily available, and are changing rapidly as feed, feeding practices, and culture methods evolve. Also, both in aquaculture facilities and in natural aquatic environment, the occurrence several diseases have emerged as a serious economic and ecological issue, and are a significant constraint to the expansion of the industry. The control of endemic diseases imposes severe year-on-year costs on producers. A global estimate of disease losses ranges about 3 to 4 billion USD per year (Stabili et al., 2010). For example, white-spot syndrome of shrimp (WSS) has cost billions of dollars world-wide. Moreover, the elimination of disease outbreaks, such as ISA (Infectious Salmon Anemia) in Scotland in 1998/1999, caused unexpected expenditure for both the industry and government (Murraya & Peeler, 2005). Even though water is the major recipient of dissolved residues from aquaculture, a considerable portion of the solid material is retained inside the ponds, discharge canals or in the vicinity of the farms. Both the culture media and coastal habitats where the activity is practiced usually shows high rates of biological activity and organic matter decomposition. Recently, particular emphasis has been directed on development sustainable approaches to coastal aquaculture. In this sense, the promotion of ecological practices to improve the ecosystem health has been highly encouraged, including water recycling, effluent management and biological treatment by integrated culture (Marinho-Soriano et al., 2011). The use of filter-feeding organisms as nutrient (inorganic and organic) extractors has proven to be a valid alternative for nutrient bioremediation. Some of the most frequently tested organisms are mollusks, which filter organic particles and phytoplankton (Marinho-Soriano et al., 2011). Integrated Multi-trophic Aquaculture (IMTA) has been proposed to achieve environmental sustainability through biomitigation of aquaculture wastes which, as compared to other accompanying methods, has advantages that may include economic stability by product diversification and risk reduction, and social acceptability through best management practices (Troell et al., 2009; Barrington et al., 2009). IMTA is a practice in which the by-products (wastes) from one species are recycled to become inputs (fertilizers, food and energy) for another through the cultivation, in the right proportions, of fed aquaculture species (e.g. finfish/shrimp) with organic extractive species (e.g. suspension and deposit feeders), and inorganic extractive aquaculture species (e.g. seaweeds) (Troell et al., 2009; Barrington et al., 2009). The reduction of microbial pollution within aquaculture can be achieved by the use of living organisms. Literature available reveals the potential capability of some invertebrates to remediate heavy metals, microbial contaminants, hydrocarbons, nutrients and persistent organic pollutants (Khoi & Fotedar, 2012; Stabili et al., 2006). Filter-feeding marine macroinvertebrates filter large volumes of water for their food requirements and exert high efficiency in retaining small particles including bacteria. The Mediterranean polychaete Sabella spallanzanii showed ability to filter, accumulate and remove from waste, bacterial groups including human potential pathogens and vibrios (Stabili et al., 2010). Licciano et al. (2005) calculated the clearance rates and filtration efficiencies for S. spallanzanii and Vibrio alginolyticus, revealing the ability of sabellids to filter bacteria with high efficiency. Therefore, sabellids are considered suitable to use in aquaculture farms as biofilters, also considering their action in removing suspended solids in waste waters to which bacteria can be attached. The aim of the present study was to assess the bioremediation potential of the filter-feeding polychaete Sabella spallanzanii, by its ability to remove bacterial groups, co-cultured with the highly valued marine shrimp Palaemon sp. Additionally, polychaete and shrimp growth was measured over time. Material and Methods In 2012, specimens of S. spallanzanii were hand collected from Peniche and Olhão coasts (Portugal) and, after an acclimatization period, they were randomly inserted in a net containing 14 individuals. The nets were inserted in an experimental recirculating aquaculture system, assembling shrimp Palaemon sp., filter-feeding polychaete S. spallanzanii and the macroalgae Ulva sp. rearing tanks. S. spallanzanii rearing tank received the wastes from the shrimp rearing tank. Their survival, growing capability and bacterial removal by filter-feeding was evaluated. The bacteriological analyses were performed using the water samples collected in the shrimp tanks at two sampling times: one time before starting water recirculation (T0), and after 21 days of experiment (T3). Bacteriological analyses included the quantitative analyses of culturable heterotrophic bacteria (22ºC), total culturable bacteria at 37ºC, culturable halophilic vibrios at 22 and 35ºC, and E. coli. Results and Discussion The results obtained in growth capability of S. spallanzanii showed an increase of 9.34% in weight, corresponding to 7.7 mg day-1, during the experiment. This could be explain due to the higher suspended solids in the culture medium. Stabili et al. (2010) reported a mean increase of total polychaete biomass of 9.0 mg day-1. Relatively to bacteriological analysis, the density of heterotrophic bacteria at 37ºC decreased substantially (Fig. 1a). The abundance of heterotrophic bacteria at 22ºC increased from T0 to T3 (Fig. 1b). This increasing density pattern of heterotrophic bacteria at 22ºC is in accordance with Stabili et al. (2010). The author stated that could be related with the effect of temperature, assessed by Pomeroy & Wiebe (2001). However, in this study no large temperature changes occur. Thus, more intensive bacteriological analyses should be done before performing any assumptions. Regarding culturable presumptive vibrios, the abundance decreased from T0 to T3 at 22 and 35ºC (Fig. 2). Regarding to E.coli, it was possible to observe a density decrease of 90% at the end of the experiment (Fig. 3). According with the decree-law n.º 236/98 of August 1st (N.º 176 – 1998), the maximum value allowable for faecal coliforms is 2000 per 100 mL, and the maximum value recommended is 100 per 100 mL. The results for E. coli stated previously are in accordance with the decree-law requirements. The use of S. spallanzanii as bioremediator of microbial pollution revealed to be efficient in a more complex culture system. The integration of this species in the culture system plays an important role since it is able to filter, accumulate and remove several bacterial groups from the water, including human potential pathogens, and thus, reduces susceptibility to disease outbreaks. For Figures and References, please consult: http://www.frontiersin.org/10.3389/conf.fmars.2014.02.00006/event_abstract

A whale shark Rhincodon typus was found in a set-net in southern Portugal in October 2011. This was the first record for continental Europe and represents an increase of the species' known range. Upwelling events and increase in sea-surface temperatures are possible reasons for this occurrence.