Plastic Busters MPAs in the lab: IEO-COB


Investigating  the potential ingestion of plastics by fish and invertebrate species

Spanish Institute of Oceanography-Balearic Oceanographic Centre


How can micro-, meso- and macro-plastics affect fish and invertebrates in a Marine Protected Area in the Balearic Islands? 

To respond to this, the IEO-COB (Spanish Institute of Oceanography-Balearic Oceanographic Centre) team is busy analyzing samples following the protocols adopted within the Plastic Busters MPAs ‘Toolkit for monitoring marine litter and its impact on biodiversity in Med MPAs’.

To begin with it, the research team has been analyzing the:

  • Stomach contents and gastrointestinal tracks of several coastal pelagic and benthopelagic species, commonly found in the National Park of Cabrera such as the Painted comber (Serranus scriba) and the Saddled seabream (Oblada melanura).
  • Stomach contents and soft tissue of several invertebrates’ species such as the Mediterranean mussel (Mytilus galloprovinicialis), the stony sea urchin (Paracentrotus lividus) and the black sea urchin (Arbacia lixula).

Serranus scriba is a subtropical marine fish (Serranidae family), grows to a length of 36 centimetres and it is a littoral, benthic species, found on rocky substrata or on Posidonia oceanica beds. The Comber’s eating preferences include crustaceans and fishes which inhabit in muddy, algal or seagrass areas. Oblada melanura (Sparidae family) specimens are around 20 centimetres long, and have a gregarious behaviour. The saddled seabream is an omnivorous fish, but feeds mainly on small invertebrates.

The mussel species Mytilus galloprovinicialis is a commercially important filter feeder which is often found attached to rocky substrates while both sea urchin species feed on both plant and animal material found on the sea bottom. All of these species are important to the ecology of the coastal waters of the National Park of Cabrera and it is extremely important to evaluate the impact that plastic marine litter is having in these marine species. 




Read more about the stony sea urchin



Read more about the Mediterranean mussel

The following steps are undertaken in laboratory in order to detect the presence and effects of marine litter in these species:


Once every sample has been weighed, a solution of 10% potassium hydroxide is added to each sample and incubated in a thermostatic bath (50 °C) . The combination of the chemicals and heat allow for a complete decomposition of all organic materials and the extraction of the litter particles.

 Digestion process for the fish and mussel samples: A) the addition of 10% KOH to a sample; 

B) samples in the thermostatic bath.


Once the samples have gone through the digestion process, the samples are then filtered using a filtration ramp and special filters to make sure the material that wasn’t completely dissolved is collected on the filter . Due to the high content of sediment in the diet of the sea urchins, the supernatant is filtered and the remaining items are separated for the third step. 

Filtration process in fume hood: A) solution of S. scriba being filtered through the filtration ramp; 

B) filtration kit, including vacuum pump.


The filters with the fish, mussel and sea urchin samples are then placed onto individual glass petri dishes and are left to dry at room temperature. Each of the filters are then analyzed under a stereomicroscope to identify the plastic items collected in each filter after the digestion and filtration process . Once these items are separated and recorded they are further analysed  with FTIR techniques in order to identify the type of polymer they are made of.

Image of the filters A) filters of M. galloprovincialis in glass petri; 

B) analysis under a stereomicroscope to identify and measure the plastic items,

 C) blue filaments in M. galloprovincialis sample.