Greek case study

Vourlias Bay (37°27'52.01"N, 23° 1'47.44"E) is a coastal area with intensive aquaculture production sites and is situated in the Peloponnesian mainland, Greece. The study area is characterized as an AZA (Allocated Zone for Aquaculture) region where several farms operating in a small bay. HCMR research team conducted a sampling in Vourlias bay in Argolikos gulf οn the 29th of June till the 1st of July (3 days). For the samplings, a HCMR research vessel, a dinghy and an auto-mobile laboratory were used that provide large laboratory space and quick sampling procedure.

The main objectives were to monitor:

  • physico-chemical features (water currents, nutrient and chlorophyll concentration)
  • toxic substances (metals, organics and antibiotics)
  • biota abundance and taxonomy (planktonic microorganisms including viruses, bacteria, eukaryotes up to mesozooplankton, benthic micro and macro-invertebrates, seagrasses, seaurchins)
  • macrofauna and phytobenthos
  • sediment chemistry and composition

FIELD WORK AND SAMPLE COLLECTION

A. Water column and community compositions

Three replicates of water samples were collected from 15 stations to validate the Aquaculture Integrated Model (AIM). Dissolved nutrients (phosphates, nitrates, silicates, ammonia), dissolved organic carbon (DOC), particulate organic carbon (POC), nitrogen (PON) and phosphorus (POP) and Chlorophyl a were measured at all stations. The effect from the aquacultures on the ecology of the water column will be evaluated under different scenarios. Furthermore, surface seawater samples were collected with the use of Niskin bottles from three stations (control ST3, ST7 and ST11), representing an unaffected system, a station under the influence of multiple farms and a station under the influence of one farm, respectively. Sampling was performed in close proximity to the fish farms every eight hours (morning-06:00, afternoon-14:00, evening-22:00) during three consecutive days (29-30th June and 1st July).

Immediately upon return to the research-vessel laboratory, sub-samples were fixed for:

  • flow cytometric enumeration of viruses and pico- and nano- plankton
  • microscopic enumeration of micro-plankton
  • assessment of mixotrophic behavior of micro-plankton

Samples were also collected for subsequent analysis of the concentration of dissolved inorganic nutrients (NO2, NO3, NH4 and PO4-3) and dissolved organic carbon. Filtration was performed for analysis of the concentration of particulate organic carbon, phosphorus and chlorophyll.

B. Toxic compounds

Meso-zooplankton was collected from 15 stations (ST1-ST15) by vertically towing a net of 200 μm mesh size three times at around 20 m depth, in order to collect adequate material for chemical and composition analysis. Sampling was performed two consequent days at 9 am to 12 am. These samples will be analyzed for metals and organic pollutants. Furthermore, seawater samples were also collected from the same stations for chemical analysis. Macro algae, sea urchins Parecentroruslividus, and seagrass were collected from two stations close to Farm 9 (Station ‘close’, station ‘far’) for analysis of toxic compounds.

C. Macrobenthos

There was a sampling of two ecosystems (seagrass and hard substrate) at the same two stations, close to Farm 9: one ‘close’ and one ‘far’ station (Figure 2) at the direction of the main water currents. The hard substrate components sampled at 0.5 m depth were: macro algae, associated macro fauna and sea urchins. We sampled for bottom water (to be analyzed for nutrients and sulfide), macro algae (to be analyzed for cover, species diversity, nutrient content (C, N, d13C, d15N, d34S) and metabolites for key species), sea urchins Parecentroruslividus (to be analyzed for cover, biomass, size, nutrient content (C, N, d13C, d15N, d34S) and metabolites) and associated macro fauna (to be analyzed for biomass and species diversity). The seagrass components sampled at 5-6 m depth were: seagrass (Cymodoceanodosa), sediment, bottom water, pore water. We sampled for bottom water (to be analyzed for nutrients and sulfide), pore water (to be analyzed for nutrients and sulphide), sediment (to be analyzed for granulometry, water content, porosity, Corg, Cinorg, TN, sulphide pools, d34S) and seagrass (to be analyzed for density, biomass, growth, nutrient content (C, N, d13C, d15N, d34S) and metabolites).

D. Sediment composition and contaminants

For the validation of the ecotoxicological models, sediment samples were collected from nine stations close to Farm 9. The sampling design included the collection of triplicate sediment samples from nine stations with three different bottom depths (30, 50 and 70 m) and three distances from the cages (0, 25 and 50 m from the edge of the cages downstream in the residual current direction). These samples will be analyzed for contaminants and benthic composition.

FUTURE SCHEDULED WORKS

A second sampling campaign will be carried out in March 2018 in the gulf of Vourlias. Sampling will last 3 consecutive days and samples will be collected from the water column and sediment for subsequent analysis. WISP station will be deployed by WI. The autonomous profiler based on the Piston-Driven Oil VB System will be tested. It is capable to perform vertical profiles from the surface down to the depth of fish farm cages. The payload is user configurable and the profiler is able to host several sensors measuring all key environmental parameters of the seawater and/or underwater camera modules in order to inspect underwater structures and components.