The port's marine ecosystem is highly disturbed by port activity and by the influence of the Barcelona coast and the of the Llobregat river mouth. The organisms that inhabit the port waters are highly conditioned by environmental factors such as water renewal, hydrodynamics and water inflows from land.
The main communities that define the port ecosystem are:
- Pelagic communities
- Benthic communities (living on the substrate)
- Bird life
- Food chain
Phytoplankton is the fraction of plankton comprising autotrophic organisms, i.e. those performing photosynthesis. Phytoplankton is the main primary producer in port waters and depends especially on stirring conditions and nutrient concentration. Sheltered waters therefore favour species of the dinoflagellate group while open waters favour diatom species.
Some of the species present in the port in the summer months can produce what is known as HAB (Harmful Algae Bloom). These species in port waters include the diatom Pseudo-nitzschia spp (carrying the ASP toxin) and the dinoflagellates Dinophysis spp (DSP toxin) and Alexandrium Catanella (PSP toxin).
Zooplankton is the fraction of plankton consisting of heterotrophic life forms (feeding on organic matter already produced by photosynthetic organisms) which are consumers at the top of the food chain, feeding on primary producers.
The Zooplankton found in the port consists of tintinnids and ciliates (single-celled organisms, or protozoa), nauplii (larvae of crustaceans) and other multicellular organisms such as rotifers and copepods.
Many species have been identified in the outer and inner port waters. These include:
- Striped red mullet (Mullus surmuletus)
- Flathead grey mullet (Mugil cephalus)
- White seabream (Dipolodus sargus i D. annularis)
- Gilt-head bream (Sparus aurata)
- Bogue (Boops boops)
- Horse mackerel (Trachurus sp.)
- European eel (Angulla anguilla)
- European conger (Conger conger)
- Black goby (Gobius niger)
- Comber (Serranus cabrilla)
- Cardinalfish (Apogon imberbis)
- Mediterranean rainbow wrasse (Coris julis)
The organisms that live attached to the substrate are called benthos and two types are to be found in the port of Barcelona, according to the substrate to which they are linked.
Soft substrat benthos: live on muddy or sandy bottoms. This community is characterised by its low mobility, adaptation to high levels of organic matter and resilience and capacity to recover following disturbance. They are considered biomarkers of the ecological status of water. Especially dominant in the sheltered waters of the harbour are polychaete annelids, which account for 70% of species, and molluscs. Percentages vary in open water, where the abundance of polychaete annelids is 25 - 50%, followed by molluscs and crustaceans.
Other groups represented are sipunculids, nemertea, nematodes, flatworms, echinoderms, cnidarians, hemichordates and chordates.
The difference between the soft substrate benthos found in sheltered waters and those found in open waters is the lower density of individuals and the lower number of species.
Hard substrate benthos: live on natural or artificial rocky substrates. Their composition is also closely linked to the quality of the water and, in particular, with turbidity and suspended matter.
There is notable presence of some coastal algae such as Dictyota dichotoma and Codium fragile.
Spirographs (Bispira volutacornis, Spirographis spallanzanii), mussels (Mytilus galloprovincialis) echinoderms (Paracentrotus lividus, Echinaster sepositum), opisthobranchs (Flavelina affinis) are among the species in the most open areas, such as the seawalls or entrance mouths.
In the more sheltered areas, in addition to mussels there are also barnacles (Balanus), ascidians (Microcosmus, Clavellina), etc.
The birds linked to port water bodies are primarily fish-eating species, which are predators in the food chain. The most common are the European herring gull (Larus argentatus) the Lesser black-backed gull (Larus fuscus), the Black-headed gull (Chroicocephalus ridibundus) and Audouin's Gull (Larus audouinii). The port is also home to a colony of Great cormorants (Phalacrocorax carbo) and the Common tern (Sterna hirundo) can often be seen fishing in sheltered waters.
The food chain in port waters interrelates the groups of organisms described above and follows a pattern of relationships as shown in the figure: