Early August 2013

Water management problems at Attika’s Schinias-Marathon National Park threaten fish populations.Schinias Marathon National Park is recently enacted protected area, a nearly peri-urban site, just 30 Km east of Athens. And Athens and Attika have few areas for aquatic biodiversity conservation, so Schinias definitely is worthy of a rigorous conservation scheme. Schinias’ “Great Marsh” is world-famous for its role in the historic Battle of Marathon (490 BC).  During the last few decades this now partially-drained marsh functioned as a military telecommunications antennae area, so this is how it was actually saved from the mega holiday-home construction boom. No-one really cared for the history or biodiversity…. Today holiday-homes and villas, green-houses and farms surround the marsh and wooded beach and the 2 km-long Olympic rowing-center lake dominates at the Park’s western edge. It is unusual that there is so much water here – and this is why it is an amazing life-rich wetland!

There is a huge karstic spring at “Makaria Pigi”, and this is the “great source” that fills the new Olympic Rowing Center Lake and once fed the “Great Marsh”. The long rectangular lake creates an interesting opportunity for biodiversity conservation. If scientifically planned and managed  the “excess water” that once was channeled straight to the sea could feed the surrounding partially-drained wetland area. And this was part of the compensatory scheme promoted during the Olympic Games rowing center development in 2004 (when the National Park was promoted). Althogh, the National Park decree was drafted in the wake of the multi-million Euro Olympic Games development is a big opportunity for nature conservation.  Surprisingly, the mitigation concept partially worked! But since no ecological water management plan was ever enforced and no one really seems to care for the wildlife values of the site- no one really knows what is going on in the “Park” in terms of biodiversity conservation. The government failed to organize the management of the park and it failed in supporting monitoring and restoration. But with the extra water, nature bloomed. Gravity sees the water through the new lake, canals, sluices and now a lot of water does end up in the Great Marsh. And the Great Marsh has noticeably revived. But this story is not just happy and “green”.

The problem

Between the Olymping Rowing Center Lake and the marsh are two simple sluices and culverts running underground (under a peri-reservoir road) to the marsh. Each sluice has a canal-like impoundment structure (water overflows from the artificial lake and rushes down into the sluice channels and then into the culverts to flow to the marsh). Fish cannot pass up to the lake and they gather under the culverts leading to the lake. The eels and other fishes that are trapped in sluice canals cannot go up into the “lake” or travel back if the culvert is clogged. So many fishes and amphibians die here each summer. A few years back (in 2010) there was an amazing fish-kill, first of Marathon Minnows (at least 5000) and then of Eels (“many thousands”). At the time our HCMR team was monitoring the Park and we tried to inform authorities with no result.

With the cooperation of the Park Managment Body, this year we visited the sluices to take a look at the situation (July 18th). We found about 500 dead Marathon Minnows and over 2000 entrapped in “Sluice 1”. About 30 writhing Eels were also visible – all trying to pass upwards into the lake. A huge Grass Snake (1.2 m. long) made an appearance. “Sluice 2” was flowing stongly with great quantities of water, the water was foamy and we could not see anything inside the sluice. Conductivity was very high 4000 μS. The freshwater fish may start to die soon in both sluice canals.

Management needed NOW!

The death of thousands of “near-threatened” and “critically endangered” fish is not the only thing that is wrong here. Of course we care for the fishes, but saving the fishes is not the only goal.

The artificial lake’s excess water needs to feed the marsh habitats for a reason: it needs to provide a “near-natural water-flow regime” that will help “ecologically restore” a suite of habitats and associated aquatic species assemblages that require specific conditions. The suite of habitats is complex – it begins with freshwater conditions and ends up in lagoon-like brackish and saline conditions – so all these must be maintained through management. Since the plain is now fragmented by the artificial lake, the sluices, canals, old-antennae facilities and in-filled road networks we need to plan for the area’s “flow-regime”.  This must be balanced by specific biodiveristy needs as well; such as specific habitat requirements for wetland-habitat specialist bird species that helped designate the area a Special Protection Area (Ferruginous Duck, Glossy Ibis etc). Also, since the Marathon plain is full of people and buildings, there is a real conflict with mosquitoes. Water management for wildlife will need to be tied-into a plan to reduce certain seasonal mosquito reproduction conditions also, and/or to manage mosquito control in an ecologically acceptable manner. Complicated, yes!

How to save the fish?

We proposed a simple fish-ladder for the fish at each sluice – a way to re-design the sluices. This is important since during drought years many many thousands of eels, minnows, mullet, sea-bass and terrapins could be entrapped and die. These mass deaths are very dangerous in terms of creating a local bio-hazard also (e.g. botulism etc). But again this is only a part of the tragedy – we need to deal with the whole. I hope we can help create a legendary protected-area at Marathon.

Reported by Dr. S. Zogaris

Location of Schinias-Marathon National Park on the east coast of Athens.

 

Detail of the Great Marsh and the Olympic Rowing Center Lake which are fed by  Makaria Spring (upper L). The blue dashed lines show the flow of water from the great Spring to the Lake and eastwards to the Great Marsh. A sandy shoreline-barrier dotted by pine forest naturally obstructs drainage and the surface water’s outlet is on the far right (just beyond the end of the photo). A suite of different wetland habitats of different salinities and conditions develops from the freshwater springs and lake (west) to the brackish and saline lagoonal wetlands (east). It is obvious how artificially fragmented the former wetland is today, so managment is necessary. Without management we will have a homogenous choatic mess – and a lot of mosquito-bitten residents against the Park!