Ecosystem function and foodwebs: critically endangered species and non-indigenous species

Key drivers
Temperature
Salinity
Ocean Acidification
Ocean Circulation
What has happened

The biggest challenge is warming, which aids the spread and establishment of warm water NIS and impacts on critically endangered species, endemic to the region. It is likely that numerous species have already been affected by climate change, but wider impacts on ecosystem function impacts are unknown.

Over 1000 NIS have been recorded in the Mediterranean, with about half introduced via the Suez Canal. Located at the eastern most, and warmest, part of the Mediterranean, the SBAs are particularly vulnerable to climate change effects and the role they play in enabling the spread of NIS. A citizen-science project recorded 50 NIS around the SBAs. 

Populations of some critically endangered endemic species in the SBAs, for example, the ghost crab and the noble pen shell, have experienced significant declines. Direct and indirect effects of climate change, including spread of NIS may have contributed to these declines.

There are also concerns about the spread of NIS in the western Mediterranean. One such invader is the silver-cheeked toadfish, which has been found to cause considerable damage to fishing nets and longlines. It is also poisonous and a potential risk to human health. The first record at the Western Mediterranean basin was recently reported at Ceuta, the Straits of Gibraltar, 28 km from Gibraltar.

In coastal areas, sea-level rise is affecting critically endangered species. For example, turtle nesting data from the SBAs indicates a potential change in nest timing, gestation periods and a gradual increase in nest flooding or wash-out events.

Many coastal and near-shore habitats are vulnerable to change, with sea temperature rise and ocean acidification threatening corals, and sea level rise likely to diminish rocky intertidal vermetid reefs. 

Seagrass meadows are vulnerable to heat waves, given they already being near tolerance limits. These meadows form the basis of the ecosystem in the SBAs and are experiencing dramatic declines, partly due to climate change acting synergistically with local stressors. 

Overall, biological community shifts and impacts on marine food webs may result from these changes.

CONFIDENCE LEVEL
LOW

Low evidence, high agreement

For Gibraltar, There is local and regional evidence of widespread colonisation, settlement and growth of the invasive algae Rugulopteryx okamurae. Information on the long-term ecological impacts is lacking. In the SBAA there is local and regional evidence of impacts of invasive species, in particular, the impacts of lionfish as well as the local mortality of Posidonia meadows.

For Gibraltar, There is local and regional evidence of widespread colonisation, settlement and growth of the invasive algae Rugulopteryx okamurae. Information on the long-term ecological impacts is lacking. In the SBAA there is local and regional evidence of impacts of invasive species, in particular, the impacts of lionfish as well as the local mortality of Posidonia meadows. 

What could happen

Impacts of climate change on native biodiversity are expected to intensify across all ecosystems from intertidal reefs to the deeper ecosystems. For example, predictions have been made that Posedonia oceanica seagrass meadows might face functional extinction by 2050. 

In Gibraltar, sea-level rise may force a shift in the distribution of endemic Mediterranean species such as the endangered limpet Patella ferruginea but impacts on populations are unknown. Climate change impacts on breeding e.g. Mediterranean Shag Phalacrocorax aristotelis desmarestii and migratory seabirds are also difficult to foresee with certainty as are the potential impacts on cetaceans that breed and feed in BGTW such as the Common Dolphin Delphinus delphis, Striped Dolphin Stenella coeruleoalba and Bottlenose Dolphin Tursiops truncatus.  

Akrotiri hosts important nesting grounds for green and loggerhead turtles. Increasing temperature could affect the ratio of males and females in the nests and thus reduce fertility rates and genetic diversity. Sea-level rise and flooding may reduce climatically suitable habitats for turtle nesting grounds. 

Sea level rise could have a negative impact on the habitats of the Mediterranean monk seal. Akrotiri area has several caves where monk seals breed, feed, and mate. Akrotiri and Episkopi cliffs are important sites for both migratory and residential birds; these are at risk from extreme events and tidal flooding. Akrotiri salt lake is also at risk from sea level rise.

Impacts from NIS are expected to be exacerbated across the region, with important implications to marine biodiversity. Projections show that climate change may cause declines in large-sized fish populations, with conditions becoming increasingly favourable for NIS.
 

CONFIDENCE LEVEL
LOW

Low evidence, high agreement

For Gibraltar, There is local and regional evidence of widespread colonisation, settlement and growth of the invasive algae Rugulopteryx okamurae. Information on the long-term ecological impacts is lacking. In the SBAA there is local and regional evidence of impacts of invasive species, in particular, the impacts of lionfish as well as the local mortality of Posidonia meadows.

For Gibraltar, There is local and regional evidence of widespread colonisation, settlement and growth of the invasive algae Rugulopteryx okamurae. Information on the long-term ecological impacts is lacking. In the SBAA there is local and regional evidence of impacts of invasive species, in particular, the impacts of lionfish as well as the local mortality of Posidonia meadows.