BSEP116B Biodiversity in the Baltic Sea - Helcom

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112 Figure 6.5.1. Integrated classification of eutrophication status based on 189 areas. Good status is equivalent to ‘areas not affected by eutrophication’, while moderate, poor and bad status are equivalent to ‘areas affected by eutrophication’. Large circles represent open basins, while small circles represent coastal areas or stations. HEAT = HELCOM Eutrophication Assessment Tool. Abbreviations: BB=Bothnian Bay, Q=The Quark, BS=Bothnian Sea, AS=Archipelago Sea, ÅS=Åland Sea, BPN=Baltic Proper northern parts, GF=Gulf of Finland, BPE=Baltic Proper Eastern Gotland Basin, GR=Gulf of Riga, WGB=Western Gotland Basin, GG=Gulf of Gdańsk, BO=Bornholm Basin, AB=Arkona Basin, MB=Mecklenburg Bight, KB=Kiel Bight, GB=Great Belt, LB=Little Belt, S=The Sound, K=Kattegat.
Large nutrient inputs in combination with long residence times mean that nutrients discharged to the sea remain in the sea for a long time, even decades, before being flushed out of the Baltic Sea into the Skagerrak and North Sea surface waters or being buried into the sediments. 6.5.2 Eutrophication status of the Baltic Sea The eutrophication status of the Baltic Sea in 2001–2006 was extensively assessed, analysed and evaluated in the HELCOM integrated thematic assessment of eutrophication (HELCOM 2009a). According to the report, the overall eutrophication status of the Baltic Sea is unacceptable. Only 13 of the areas assessed in the report were classified as being ’eutrophication non-problem areas’, while 176 areas were classified as ‘eutrophication problem areas’. The non-problem areas were found in the Gulf of Bothnia and in the Kattegat (Figure 6.5.1). The overall view, however, is not completely dark because nutrient inputs to the Baltic seem to have decreased slightly from 1995–2000 to 2001–2006. In most sub-basins, the highest surface concentrations of nutrients were observed in the 1980s and during the past two decades there have been encouraging signs of decreasing surface nutrient concentrations in many of the sub-basins. a major problem in the Baltic Sea. Harmful algal blooms represent periods of reduced biodiversity and the toxins produced by algae are a threat to other organisms. Extensive seagrass meadows and perennial macroalgal communities harbour the highest biodiversity found in coastal shallow-water areas. In the HELCOM Red List of Marine and Coastal Biotopes and Biotope Complexes, eutrophication was considered to be the main threat, along with general pollution, to the marine and coastal biotopes and biotope complexes of the Baltic Sea (HELCOM 1998). Eutrophication has complex effects on the state of submerged aquatic vegetation: (1) reduced light penetration through the water column, caused by increased pelagic production, limits the depth penetration of submerged species such as eelgrass and bladder wrack; (2) increased sedimentation can prevent the settlement of new specimens on the seafloor and reduces the amount of suitable substrate to be colonized by perennial species on all types of substrates; and (3) the excess of nutrients during the whole vegetation period often favours opportunistic species with short life cycles and rapid development over the perennial species with lower productivity, causing a shift in community composition. 6.5.3 Effects of eutrophication on biodiversity Eutrophication has direct as well as indirect negative impacts on biodiversity. The manifestations of the large-scale eutrophication problem are well known in most parts of the Baltic Sea; these include turbid water caused by high quantities of planktonic algae and other planktonic organisms, mats of macroalgae stranded on shores, reduced distribution of benthic habitats such as eelgrass meadows, or oxygen depletion resulting in the death of benthic animals and fish. The abundance of phytoplankton reflects the productivity of the planktonic ecosystem. Phytoplankton blooms in spring and summer are periods of naturally high production supplying energy to the ecosystem. However, excessive algal blooms and especially blooms of harmful algae, such as cyanobacteria or certain haptophytes, are The composition of animal communities living on the seafloor of the Baltic Sea reflects the conditions of the environment. In the eutrophication process, broad-scale changes in the composition of the communities usually accompany the increasing organic enrichment of the sediments. At advanced stages of eutrophication, oxygen depletion becomes common. In many areas of the Baltic, the seafloor animals are exposed to widespread oxygen depletion or even complete anoxia. As a result, the biodiversity on the seafloor is reduced or animal communities are completely destroyed if anoxia is long lasting (see also Chapter 3.4, Benthic invertebrate communities). Permanent anoxia is common in deep, permanently stratified basins of the Baltic Sea, such as the Gotland Basin. In shallow areas, oxygen depletion mainly occurs seasonally. The effects of eutrophication are also manifested in fish communities. In principle, eutrophication 113
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Baltic Sea Environment Proceedings
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Published by: Helsinki Commission K
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TABLE OF CONTENTS PREFACE . . . . .
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6.6 Hazardous substances . . . . .
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1 INTRODUCTION 8 1.1 An integrated
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Box 1.1. Biodiversity The term biod
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of saline water from the North Sea
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14 On a global scale, marine ecosys
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Box 1.2. Regime shifts in the Balti
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2 MARINE LANDSCAPES AND HABITATS 18
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From an ecological point of view, a
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Box 2.1.2. The Baltic marine landsc
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• A coherent data set on benthic
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Denmark Estonia Finland Germany Lat
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Mud-sandflat, Greifswald Lagoon, Ge
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3 COMMUNITIES Communities are assem
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32 Spring bloom index 1200 1000 800
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34 Unusual events and new species i
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36 Depth limit (m) the Gulf of Both
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Number of species 16 14 12 10 8 6 4
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Figure 3.2.7. Left panel shows pred
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Implications for the Baltic Sea Act
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Biomass (wet weight, mg per m 2 ) B
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the other hand, is not selected by
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iomass can be used to assess enviro
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Average number of species 20 15 10
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52 Macoma baltica where the influen
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the total BT identified for each ma
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Recruitment (thousands) 8000000 700
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Alien species Several alien fish sp
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4 SPECIES The number of species in
Page 64 and 65: Table 4.1.1. Results of dedicated a
Page 66 and 67: Number of stranded porpoises 180 16
Page 68 and 69: is recommended to survey harbour po
Page 70 and 71: Number of individuals 12000 10000 8
Page 72 and 73: Mean blubber thickness (mm) 40 35 3
Page 74 and 75: Breeding pairs 60000 50000 40000 30
Page 76 and 77: predation on nests and nesting adul
Page 78 and 79: sites outside the Baltic, decreased
Page 80 and 81: Table 4.3.1. Development of the pop
Page 82 and 83: 80 Number of breeding pairs 3000 25
Page 84 and 85: The strategic goal of the BSAP to h
Page 86 and 87: for a given site or area. The secon
Page 88 and 89: Mussel bed reef community, Jasmund,
Page 90 and 91: Table 5.3. Assessment results of th
Page 92 and 93: Aerial photo of harbours seals (Pho
Page 94 and 95: 6 HUMAN PRESSURES ON BIODIVERSITY A
Page 96 and 97: Table 6.1.1. Catch range during the
Page 98 and 99: Baltic herring trawling, Bothnian B
Page 100 and 101: 6.1.3 Major international framework
Page 102 and 103: 100 Oil turnover (millions of tonne
Page 104 and 105: NOx emissions and sewage Macrophyte
Page 106 and 107: Communication links There are a num
Page 108 and 109: Figure 6.3.3. Left: concrete-stone
Page 110 and 111: ecommendations would contribute to
Page 112 and 113: Tourist fishing 110 cial fishery fo
Page 116 and 117: can be considered as having been a
Page 118 and 119: Although no direct, dramatic mass m
Page 120 and 121: Bearing in mind the complex hydrogr
Page 122 and 123: Box 6.7.1. Invasion status of the B
Page 124 and 125: Table 6.7.1. Examples of ecological
Page 126 and 127: munities that formerly consisted of
Page 128 and 129: 6.8.2 Activities generating noise i
Page 130 and 131: 128 and fish in the Baltic Sea area
Page 132 and 133: 800 700 600 bag of the two German B
Page 134 and 135: Fish swarm on kelp (Laminaria sp.)
Page 136 and 137: tion of ice cover, either through r
Page 138 and 139: 7 STATUS OF THE NETWORK OF MARINE A
Page 140 and 141: Box 7.1. Natura 2000 network of pro
Page 142 and 143: 25 20 on how the criteria on ecolog
Page 144 and 145: estrial, nearshore marine, and offs
Page 146 and 147: 144 >30 psu 18-30 psu 11-18 psu 7.5
Page 148 and 149: Permission needed Restricted Forbid
Page 150 and 151: Figure 7.8.a. MARXAN ’best portfo
Page 152 and 153: The BSPA network is relatively well
Page 154 and 155: Mammals. Among the mammals, the pop
Page 156 and 157: 154 taxonomic groups and communitie
Page 158 and 159: 156 provided by an ecosystem. Use o
Page 160 and 161: 158 Reduction of human pressures Wh
Page 162 and 163: 160 fishing on fish population dyna
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162 Baden, S., Boström, C. (2001).
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164 Season 2001-2002. Acta Zoologic
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166 Gasiūnaitė, Z.R., Cardoso, A.
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168 HELCOM & OSPAR (2003): Joint HE
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170 ICES (2008c). Report of the Bal
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172 area: density-dependent effects
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174 Noer, H., Clausager, I., Asferg
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176 Scheffer M., Carpenter S.R., Fo
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178 by passive acoustic monitoring.
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180 Warzaw, Poland Vilhunen, Jarmo,
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182 6.7 Alien speices Authors: Lepp
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ANNEX III: CONSERVATION STATUS OF T
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ANNEX IV: HABITAT OR SPECIES DISTRI
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ANNEX V: STATUS OF BREEDING AND WIN
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BSEP116B Biodiversity in the Baltic Sea - Helcom

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