Экологический кризис прибрежной зоны. Тезисы Верищагинской конференции

ECOLOGICAL CRISYS IN THE COASTAL ZONE OF LAKE
BAIKAL
Timoshkin O.A., Malnik V.V., Sakirko M.V., Bondarenko N.A., Rozhkova N.A., Sheveleva N.G., Volkova E.A., Nepokrytykh A.V., Zaitseva E.P., Medvezhonkova O.V., Lukhnev A.G., Zvereva Yu.M., Poberezhnaya A.E., Shirokaya A.A., Potapskaya N.V., Tomberg I.V., Domysheva V.M., Timoshkina E.M., Kupchinsky A.B.

Limnological institute SB RAS, Irkutsk, Russia
tim@lin.irk.ru

Interdisciplinary research of Baikal coastal zone (splash zone including) has been performed within 2007-2014. Significant changes of the structure and quantitative characteristics of the shallow water benthonic communities were detected at the scale of the entire lake (Timoshkin et al., 2014 - most

References can be downloaded from www lin.irk.ru). During 2007-2012 it has been performed sporadically, in restricted areas of Bolshye Koty and Listvyanichny bays only, due to lack of financial support (Kravtsova et al., 2011; Timoshkin et al., 2014; Kravtsova et al., 2014). Methods and main results of the ecology of splash zone investigations were published in 13 papers (for review, see: Timoshkin et al., 2011). Taxonomic composition and quantitative characteristics of macrophyto-, macrozoobenthos, plankton communities, as well as hydrochemical, hydrological and microbiological parameters of the near-bottom and surface waters were investigated in the shallow water zone. Several round-Baikalian spring-summer and autumn expeditions were organized since 2013, due to initiative of acad. Grachev M.A.
When these processes started? Or - when they were expressed most remarkably? For lack of the regular round-Baikalian survey of the shallow water communities before 2010, one can provide only approximate answer, based on the limited research in South Baikal. Most probable starting point is 2010¬2011. Most significant changes detected in the macrophytobenthos communities. Conclusions on possible changes of the macrozoobenthonic communities (except for sponges, see below) can be made after on¬going quantitative sample analysis only. Chronology and brief characteristics of these unusual and/or negative ecological processes, which have been found within 2010-June 2015, are given below.

1. Two independent groups of experts (ob. cit.) reported on significant, large-scale modifications in composition and productivity of the dominant macroalgae, detected in 2010-2011, in two local South Baikal bays (Bolshye Koty and Listvyanichny). Mass development of non-typical for open Baikal green filamentous algae of Spirogyra genus (at 0.5-10 m depths) and abundant late autumn bloom of another filamentous algae Stygeoclonium tenue, in the shore line zone (first algal belt), which usually occupied by Ulothrix zonata filaments. Later on (2013-2014) Spirogyra mass blooming was detected in the shallow water zone at the scale of almost entire lake: Severobaikalsk and Nizhneangarsk cities; Onokochanskaya, Boguchanskaya, Senogda, Ludar’, Ayaya, Amnundakan, Davshe, Bargyzin (northern coast, off Maximikha, Rovesnik etc.) bays; Babushkin, Tankhoy, Baikalsk, Slyudyanka, Kultuk cities; old Baikalian railway, Listvyanichny, Obuteikha, Bolshye Koty, Bolshoe Goloustnoe, Peschanaya, Babushka bays. It means, that Spirogyra spp. massively developed and even dominated in the shallow water zone of the eastern, and in many areas of the western coasts. As distinct of comparatively shallow eastern coast with more or less homogeneous distribution, algal blooms along the western coast have been strictly concentrated opposite of the coastal settlements and the centers of recreation activity. Surprisingly enough, the development maximum of Spirogyra is detected during the autumn (September-October) with low water temperatures (4-8° C). Two areas (Listvyanichny Bay and Tyya-Senogda coast) of 15-20 investigated so far are characterized by all-the-year round mass bloom of Spirogyra spp. Drudge samplings, performed in Boguchanskaya Bay and opposite of Tyya River mouth (autumn 2013), evidenced, that the Spirogyra filaments are quite abundant till 10-20 m depth. Wet biomass of the alga varied within 100-1500 g/m2, what is compatible and even higher of the analogous indexes known for Baikalian algae of the 1-st and 2-nd algal belts. Late autumn Stygeoclonium mass bloom was typical for the 1-st algal belt in 2013, as well as in 2014 in many areas of all 3 basins.

2. Significant increase of the typical Baikalian macroalgae wet biomass (productivity) in the shallow water zone. For example, the algal biomass of the 1-st belt (with U. zonata dominating, June 2015) in some areas of North basin varied within 3-5 kg/m2, what is much higher of the analogous indexes known for the former times (Ижболдина, 1990: maximum in June - 0.5 kg/m2).

3. Mass development of the «saprophytic» (see below) and «free-living» blue-greens in several areas of the lake. Significant amount of the Oscillatoriales filaments have been found in the drudge benthonic samples, taken from 10-15 m southern of Peschanaya Bay, in summer of 2013 and 2014. Their mass blooming found as well in the shallows of Bolshye Koty, Barguzin bays, etc. (Phormidium, Oscillatoria, Tolypothrix spp. and others).

4. Giant coastal accumulations of rotten algae (Spirogyra, Elodea and other higher water plants, blue-greens, Cladophora glomerata etc.), wet biomass of which may exceed 90 kg/m2, detected within 2013-2014 at the first time. They are located in the splash zones of Tyya-Senogda beach, Chyvyrkuy (Monakhovo) and Barguzin (Maximikha, Rovesnik) bays, MRS, Shida Bay and Kultuk coast. Abundant coastal accumulations, mostly consisting of the “free-living blue-greens” (Tolypothrix spp., etc.) detected in Barguzin Bay at the first time. Giant algal accumulations on the coasts are typical for the late summer or autumn seasons. However, one of them (consisting of typical macroalgae of this area) was found unusually early - in June 2015, opposite of MRS settlement, at the first time. Evidently, seasonal maximum of the local algae development may occur earlier than before.

5. Mass Gastropoda extinction (mostly - representatives of Lymnaea genus) is described in 2013¬2014: billions of the died shells found on the sandy beaches between Tyya and Senogda. These “cemeteries” are located along the areas of the most abundant Spirogyra development and influenced by sewages from Severobaikalsk City. Less abundant Lymnaea shell accumulations found along the splash zone, off Maximikha settlement in Barguzin Bay (June 2015).

6. Mass extinction and several kinds of diseases of endemic Lubomirskiidae sponges at the scale of the entire lake were described in 2013-2014 (Тимошкин и др., 2014). All 3 ecological forms of the sponges (branched, encrusting, globular) can be sick. Over than 50 dives performed in 2014. Depending on area, from 30 to 100% of branched Lubomirskia baikalensis specimens were either sick or damaged and died. According to Dr. Ch. Boedecker (pers. comm.), in most of the studied areas of South basin (September 2014) this process was limited by isobaths 15-20 m. Deeply leaving sponges were found to be sick in June 2015.

It was described, that the most distributed sponge illness is accompanied by mass development of the “saprophytic” blue-greens of Phormidium genus (Тимошкин и др., 2014). The filaments are cherry- red and moving. Light-microscopic analysis evidences, that each affection patch on the sponge surface consists of 1-2 dominating blue-green species (90-95%). Different deformations and damage of the external sponge surface (=beginning stages of its extinction) in most cases (50-80%) happen prior to the mass blue-green development. According to preliminary data, the branched sponges, dwelling in the South Basin (Listvyanichny, Bolshye Koty Bays, off Chernaya River mouth) are most of all affected by illness. Much less damaged or even healthy L. baikalensis specimens were found around the north¬western coast area, approximately located between Elokhin Cape and Bolshye Olkhonskye Vorota Gate. Nota bene: the same coastal area has been found to be free of mass Spirogyra blooms in 2014.

7. High concentrations of the fecal indicating bacteria have been determined in the surface and near-the-bottom water layers along the coasts opposite the settlements. The same is true for the interstitial waters (especially - under the coastal accumulated algae) of the splash zone. For example, the enterococci concentrations may exceed 2000 colony forming units per 100 ml.

Results of 13-years long investigations evidencing on the large-scale, so-called "hidden" (or - indirect) eutrophication of the splash and the shallow water zones of Baikal (Timoshkin et al., 2014; Timoshkin, 2015). Huge amount of the pure waters and the active turbulence prevent the creation of the stable areas or patches with high nutrient concentrations in the water column (what is typical scenario of eutrophication in many shallower and smaller lakes). Extra nutrients entering Baikal coastal zone through the inlets (1) and, what is typical for most of the settlements without sewage purification system, through the coastal ground, by passive filtration (2). Therefore, the most illustrative ecological changes happen in the near shore zone and related to shallow water benthonic (bottom) rather than planktonic (water column) communities. According to preliminary data for 2012-2014, sewage of Severobaikalsk only contributed into the shallow waters of the north top of the lake up to 6 tons of P (PO4-) annually. It was the main reason of the most abundant Spirogyra bloom ever detected during all history of limnological research on Baikal. Total wet biomass of costal accumulated algae (95-97% of Spirogyra), detected along to 8 km of Tyya-Senogda beaches in autumn 2013, exceeding 1400 tons.

According to the senior author, the main reasons of the negative ecological processes described are as follows: a) long-lasting discharge of non-properly purified (or not purified at all) sewages into shallow water zone (Severobaikalsk, Babushkin, Baikalsk, Slyudyanka and other cities); b) destroyed purification stations, which were constructed during the USSR period (Ust-Barguzin) or their absence in the largest coastal cities and settlements, where the active construction of the hotels and recreation centers is taken; as a result -passive sewage filtration through the ground into the coastal zone; c) mass discharge of the sewage from the numerous ships and vessels. According to the world literature (for review, see Timoshkina, in press), mass Spirogyra bloom is often accompanying the areas with non-properly purified sewage discharge. Two other factors such as artificial water level fluctuations and climatic changes may be crucial for the mass development of the macrophytes. All the factors are detected in Baikal. However, to the mind of the senior author, climatic changes may only catalyze these processes, but barely can play the dominant role. Extra nutrient income should be considered as the most important factor of mass algal blooms.

All these negative phenomena observed in the lake for the past four years, have not been documented and are not reflected in the government reports on the state of the ecosystem of Lake Baikal in 2011-2014. This situation clearly shows the inefficiency of government monitoring system of Lake Baikal because it is almost exclusively concentrated on the survey of the central water body of the lake. Shallow water zone (and splash zone), which are the most indicative from the viewpoint of potential anthropogenic influence, are not included into the monitoring system. Therefore it is not in principle capable of diagnosing the possible destruction of the ecosystem bottom occurring due to the “hidden” eutrophication.

Investigations performed within the federal project № 01201353447 «Current condition, biodiversity and ecology of the coastal zone of Lake Baikal» and partly supported by RFBR project № 13-04-01270 and by director of the Institute, academician, Grachev M.A.