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Threats and Answers | CONVIVE LIFE

PROPOSED PLAN OF ACTION

Hydrodynamic alterations

One of the most important and frequent threats to Atlantic estuaries is the alteration of the hydrodynamics in areas that are isolated from the other parts of the estuary by way of dams. These types of infrastructures can be seen in the estuaries of Oyambre, Tina Menor and Joyel, which were built for the exploitation of natural resources (tree plantations, aquaculture, tide mill).
Related Issues
The reduction and/ or modification of the tidal flow which penetrates through the existing openings in the dams, either with fixed (e.g. Oyambre) or motorised gates (e.g. Tina Menor and Joyel’s tidal mill), and the blockage of water flows (the Joyel Lagoon) cause changes in the physical condition of the pond and, therefore, in the habitats of community interest. Specifically, the modification of the natural flooding process caused by the tides, the salinity status and the renewal of the water have an impact on the sandbanks which are slightly covered by sea water all the time (habitat 1110), estuaries (1130), mudflats and sandflats not covered by sea water at low tide (1140), Atlantic salt meadows (1330) and Mediterranean and thermo-Atlantic halophile scrubs (1420).

Recovery plans of action

The actions leading to the recovery of the hydrodynamic balance of estuaries (actions A.2, A.3, A.4 y C.2.) consist of:

  • Increase of the opening of the Zapedo dam so that the tidal water flow can penetrate into the internal areas of the Capitan Ria (Oyambre).
  • Regulate the opening and closure of the gates to modify the necessary water renovation system for environmental recovery at Tina Menor and Joyel. Such hydraulic regulation system is compatible, at the same time, with the development of the socio-economic activities (e.g. aquaculture in Tina Menor and didactic activities at the tide mill of Joyel) and environmental activities.

Presence of invasive species

A threat of high relevance for estuaries is the presence of invasive species. At the Capitan Ria (Oyambre Estuary), at the Tina Menor pond and the Joyel and Victoria Lagoons, the invasive species Baccharis halimifolia competes and displaces the autochthonous vegetation of the high marsh, specifically the Atlantic salt meadows generally predominant with reeds.
Related Issues

The hydraulic regulation provided by dams at the marshes contributes to the settlement and growth of Baccharis halimifolia at estuaries, at the same time as limiting the settlement and growth of the natural vegetation communities. The development of this species causes the alteration of the structure and composition of the habitats of community interest, especially of Atlantic salt meadows (1330) and Mediterranean and thermo-Atlantic halophile scrubs (1420), the biological communities of which are altered by the presence of it. As a consequence of such alterations, the preservation status of both habitats is poor in the framework of the Natura 2000 network of Cantabria. These dramatic changes to the habitat and the species caused by the B. halimifolia can have a direct effect on the stopover strategies of bird migration with severe consequences for their preservation.

 

Recovery plans of action

The activities leading to the recovery of habitats 1330 and 1420 in the estuaries (Actions A.1 y C.1.) consist of:

  • Removal of individuals belonging to species B. halimifolia at Tina Menor, Oyambre, Joyel and Victoria. This activity in combination with those described to recover the tidal system of the estuary will reduce or prevent the species from returning and will keep it under control in the long run.

 

Contaminating spillage into the environment

A frequent threat posing a risk to the preservation of the habitats of community interest and the species is the contaminating spillage. This source of pressure is registered at the Tina Menor Estuary, amongst other places, where specific treated spills come from the water circuit of the Tina Menor S.L. fish farm.

Related Issues

The alteration of the environment on account of spills could generate specific episodes of eutrophication and changes in the specific composition of the vegetation that could lead to the alteration of the habitats of community interest.

 

Recovery Plans of Action

The recovery activities aiming to reduce the effect of the spillage of sewage water into the estuaries (Actions A.3, A.4 y C.3.1.) are the following:

  • Completion of the sewage water treatment system of fish farm Tinamenor S.L. before the spills into the environment, by means of an artificial wetland pilot system made up of typical communities.

Eutrophication of the environment

The most significant threat that can affect the preservation and biodiversity of estuaries is eutrophication. This type of pressure is identified in Tina Menor, Victoria and Joyel. It is characterised by a mass proliferation of phytoplankton and/ or green algae (e.g. green algae cover approximately 50% of the area of the Santa Olaja pond in Joyel), as a consequence of the dynamics of nutrients under conditions of low water renewal. Such rate of renewal is subject to the regulation of the gate opening system of the dam at Joyel and Tina Menor.
Related Issues

Amongst the impacts from the eutrophication process we can highlight its effect on the preservation status of the habitats of community interest existing in the lagoons, such as sandbanks which are slightly covered by sea water all the time (habitat 1110), estuaries (1130), mudflats and sandflats not covered by sea water at low tide (1140), Spartina swards (1320), Atlantic salt meadows (1330) and Mediterranean and thermo-Atlantic halophile scrubs (1420). Specifically, habitat 1420, the preservation status of which is poor in the framework of the Natura 2000 network, is highly sensitive to eutrophication of the environment. Eutrophication also puts at risk the preservation of the habitat of species using this lagoon.

 

Recovery Plans of Action

The recovery activities aimed at the reduction of the impact associated to the eutrophication processes in estuaries (Actions A.1, A.2, A.3, A.4, C.2 y C.3.2.) consist of:

  • Suppression of the proliferation of green algae growing inside the Joyel mill pond.
  • Recovery of hydrodynamic performance in order to contribute to the regular renewal of the water at Tina Menor, Oyambre and Joyel.
  • Reduction of the organic content of the sewage water spills originated by sewage treatment company Tinamenor S.L.