Posidonia oceanica meadows are probably the most essential organic communities within the Mediterranean. In some portions of the coast of Ibiza, they’re nonetheless in depth and structurally nicely preserved, thank you largely to extensive knowledge dissemination paintings during the last many years.
The dangerous information is this state of excellent conservation known in some portions of the island isn’t all the time a sign of excellent ecological standing. When inspecting the fish communities related to those meadows, the truth is extra advanced and worrisome.
Posidonia Ocean Prairie. CC BI Censuses of fish.
The visible fish inventories we performed as a part of the MarPitius25 Aula Ibiza Preservation of Blue Criminology undertaking of the Jaume I College display that, even in well-developed meadows, aquatic communities can provide a low explicit richness – the whole selection of species within the habitat. Moreover, its abundance – the whole selection of people of a specific species found in a given space, group or ecosystem – and its biomass – the whole quantity of dwelling natural subject in a space – are not up to what can be anticipated for this kind of habitat.
This distinction between the nice look of the habitat and the organic reaction raises related questions on the real functioning of the coastal ecosystems in Ibiza.
Pisces have so much to mention
Our analysis undertaking started through undertaking a fish census for a systematic analysis of the cumulative have an effect on on Ibiza’s coastal waters.
Posidonia oceanica meadows are precedence habitats and are specifically delicate to anthropogenic pressures, similar to salinity, turbidity, city effluents and different adjustments related to extensive coastal use. Subsequently, the fauna that this precedence habitat can accommodate is a right away organic indicator of the state of the ecosystem.
The sphere paintings used to be performed in June 2025, which coincided with a duration of prime power at the coast of Ibiza. We selected 3 learn about spaces – Santa Eularia, Cala Sol d’en Serra and Talamanca – because of their ecological and social significance, in addition to their proximity to shops – pipelines for the shipping of in part handled wastewater to discharge spaces, that are basically positioned at sea – and spaces that acquire other anthropogenic affects.
Sampling, performed through the Denia Marine Laboratory of the Multidisciplinary Institute for the Setting “Ramon Margalef”, College of Alicante, used to be performed via visible surveys with self reliant diving.
Researchers Cesar Bordehore (left) and John Dobson, right through the implementation of the undertaking within the waters of Ibiza. Eva Fonfria and Esteban Morelle-Hungary Low richness and biomass
A complete of three,243 people belonging to fifteen species have been assessed, along with the class registered as “unidentified juveniles”. By way of locality, 12 species have been found out in Cala Sol d’en Serra, 12 in Talamanca and 11 in Santa Eularia.
The communities have been numerically ruled through a small workforce of 5 species, amongst which Chromis chromis, Oblada melanura, Sarpa salpa, Coris julis and Boops boops stood out. In the meantime, different species seemed with a lot decrease abundance.
Salema (Sarpa jedra). Diego Delso / Wikimedia Commons., CC BI
On the native degree, standardized way display spatial variations however a not unusual trend of somewhat low biomass for well-preserved Posidonia oceanica meadows.
The record itself emphasizes that some social species may give abundance and biomass with out essentially reflecting a structurally advanced group, which is why it is very important to research their whole assemblage—a subset of taxonomically comparable species that coexist at a specific position and time.
Predominance of small sizes
In the entire sampled stations, a transparent predominance of small people is noticed, adopted through an especially decreased presence of adults.
This trend, which is continually repeated within the 3 learn about spaces, is especially putting as it used to be recorded in structurally well-preserved grasslands.
From an ecological standpoint, this mix might counsel that, even supposing the habitat maintains its bodily integrity, it does no longer serve as as an area in a position to maintaining fish populations with an entire construction.
The effects record means that the low presence of bigger specimens could also be because of the truth that those people trip to different spaces or live to tell the tale outdoor the sampled spaces, slightly than last inside them. In the end, the noticeable result is a group ruled through small sizes and with decreased international biomass.
Not like different spaces of the Mediterranean
To contextualize those effects, the learn about compares them with an identical sampling performed at the coast of Denia (Alicante). Even supposing the record itself cautions that a couple of transects have been made there and that direct comparisons will have to be interpreted with warning, the whole distinction is obvious.
A better selection of species, a better presence of species of business passion and a extra balanced measurement construction have been recorded in Denia. Whilst in Ibiza 97.6% of people corresponded to the small measurement class, in Denia this proportion used to be considerably decrease. Biomass and variety have been additionally upper at the continental coast.
This distinction reinforces the translation that the coast of Ibiza could also be in a compromised scenario, in keeping with the larger depth and accumulation of pressures described within the MarPitius framework25. This interdisciplinary initiative seeks to diagnose the cumulative have an effect on of discharges from desalination vegetation, wastewater remedy vegetation and different pollution at the coastal waters of Ibiza, from a systematic, criminal and ecological point of view.
The conclusions of this learn about aren’t restricted to describing the precise scenario, but additionally level to the want to enforce a tracking community. The record emphasizes that it will be significant to copy censuses in several seasons and over a number of years to resolve temporal variability. On this approach, it’s going to verify whether or not the noticed patterns are maintained and can assist to know the way the construction of fish communities evolves.
Handiest via steady tracking is it conceivable to as it should be determine essentially the most appropriate spaces for the advent or demarcation of secure marine spaces and thus assess whether or not the security measures applied successfully give a contribution to their restoration.
Out of appears
Now revealed effects display that structural conservation of Posidonia oceanica meadows in itself does no longer ensure excellent ecological functioning of the analyzed device.
Communities with low biomass content material and decreased fish presence, in comparison to different spaces, might constitute a caution sign that isn’t all the time visual to the bare eye.
On this state of affairs, the inclusion of organic signs similar to composition, measurement construction and biomass of fish communities in coastal control will let us locate cumulative anthropogenic results prior to injury turns into irreversible.
And keeping the ocean is not only about keeping up its look: it will have to be ensured that ecosystems serve as totally and sustainably in the longer term.
