BSEP116B Biodiversity in the Baltic Sea - Helcom

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Mammals. Among the mammals, the population of harbour porpoise, especially in the Baltic Proper, is in a precarious state and the status of ringed seals is still unfavourable. The grey seal population has increased steadily since 1988, but the recovery of grey seals south of 59° N, where they were regularly present before they were hunted to extirpation in the beginning of the 20th century, is still very slow. Fisheries by-catch and prey depletion are among the most prominent and continuing threats to these populations, while the impacts of hazardous substances on seals have been reduced. 152 Bubbling reef, Kattegat Sea. The increased prevalence of oxygen-depleted deep water is perhaps the single most important factor influencing the structural and functional biodiversity of benthic communities in the open-sea areas of the Baltic Sea. Fish. Since the mid-1980s, the Baltic fish community has undergone a shift from a dominance of demersal communities to clupeids. The shift was caused by a combination of natural (i.e., climate variability) and human-mediated factors such as eutrophication and fishing. In a number of coastal areas, species benefiting from or tolerating eutrophication such as percids and cyprinids are currently flourishing. Warm summers may also have contributed to this development. In many areas, fish stocks have declined owing to high fishing pressure. Several stocks of migratory fish species are in a poor condition because of damming or blocking of migratory pathways. Birds. Among the bird species assessed, a longterm population decline is evident for dunlin, as well as a recent decline for eider and long-tailed duck. The causes behind these declines are not well understood, but climate change (in the case of the dunlin), and shipping-induced oil spills, fisheries by-catch and habitat deterioration (in the case of the ducks) may have contributed to the decline. Alien species. About 120 alien species have been recorded in the Baltic Sea since the early 19th century. So far, alien species have mostly had an impact in coastal areas, while there are only a few alien species that have been introduced into the open-sea environment. Certain coastal lagoons, especially in the southern Baltic, have been heavily impacted by introduced species. Most of the observed alien species that have spread to the Baltic Sea have not yet become invasive and have, in fact, enriched the species and functional biodiversity of the Baltic Sea. However, new introductions pose a threat to the entire ecosystem and its functions, and the risk of new invasions remains high. Threatened and declining species. There are currently 59 species that are considered as threatened or declining in the Baltic Sea. The only known extirpated species is the sturgeon. All mammals are under threat or in decline, at least in some parts of the Baltic. The largest single group of threatened or declining species is fish and lampreys, which includes 23 species. Biotopes. Coastal biotopes and habitats are largely in an unfavourable conservation status and continue to be under increasing pressure in many sub-regions. Many, if not all, habitats are impacted by eutrophication. In addition, physical disturbances such as dredging, disposal of dredged material, and construction of structures or installations are rated as major pressures on these coastal habitats. The poor environmental status of the habitats has implications far beyond the local scale because the habitats are important living, feeding, reproduction and nursing environments for associated flora and fauna.
The Baltic Sea biodiversity is inherently sensitive to disturbances owing to its relatively limited number of species, low genetic variation, and few species within important functional groups. Deterioration of the status of biodiversity, as manifested by the decline of communities and key species, is critical because it diminishes the resilience or buffering capacity against large-scale shifts in the Baltic Sea ecosystem and increases the risk for escalating deterioration of the environment. Signs of improvement: The protection of threatened species has been a central theme in nature conservation in the Baltic Sea area since the 1950s and improvements have been achieved among bird and mammal populations that have been subject to protective measures. Birds. The previously threatened white-tailed eagle and great cormorant show considerable increase in population size, particularly in comparison to the beginning of the 1980s. improvement in the natural smolt production of certain salmon populations, improvement of sea trout populations in the western Baltic, significant improvement of the smelt stock in the Gulf of Riga, and an increase in the share of piscivorous fish and the trophic level of fish communities in some coastal areas. Aquatic vegetation. In a number of coastal areas of the Baltic Sea, e.g., in the northwestern and northeastern Baltic Proper, submerged aquatic vegetation is showing signs of recovery after years of deterioration. These improvements show the results of restrictions or bans on hunting, reductions in inputs of certain hazardous substances, protection of important habitats, biotopes and species and, to some extent, improvement in water quality. The improvements also show that concerted and inter-sectoral management actions have reversed the precarious state of certain species in the Baltic Sea to a better status. Grey seals. The population of grey seals in the northern Baltic Sea is increasing at rates almost maximal for the species. Fish. There are several positive signs for Baltic fish in recent times. These include, amongst others, an A crude Baltic-wide overview of the conservation status of Baltic biodiversity was compiled based on the status of some of the elements of biodiversity, mainly species and communities addressed in this assessment with sufficient data availability (Table 8.1). Favourable conservation status of species, Table 8.1. A crude Baltic-wide overview of the conservation status of biodiversity in approximately 2000– 2006 in the different sub-regions of the Baltic Sea presented as an estimation of favourable (green) or unfavourable (red) conservation status of different elements of biodiversity based on the information compiled in this assessment report and expert judgement. NA – Not applicable, ? – data not available. Biodiversity element Kattegat and Danish Straits Southern Baltic Proper Northern Baltic Proper Gulf of Riga Gulf of Finland Gulf of Bothnia Benthic invertebrate ? ? communities Harbour porpoise NA NA Grey seal Ringed seal NA NA Harbour seal NA NA NA NA White-tailed eagle Cormorant Long-tailed duck NA NA Dunlin Bladder wrack NA Eelgrass ? ? NA Charophytes ? Pseudocalanus ? NA Acartia Temora NA Limnocalanus NA NA 153
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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
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Table 4.1.1. Results of dedicated a
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Number of stranded porpoises 180 16
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is recommended to survey harbour po
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Number of individuals 12000 10000 8
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Mean blubber thickness (mm) 40 35 3
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Breeding pairs 60000 50000 40000 30
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predation on nests and nesting adul
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sites outside the Baltic, decreased
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Table 4.3.1. Development of the pop
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80 Number of breeding pairs 3000 25
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The strategic goal of the BSAP to h
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for a given site or area. The secon
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Mussel bed reef community, Jasmund,
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Table 5.3. Assessment results of th
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Aerial photo of harbours seals (Pho
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6 HUMAN PRESSURES ON BIODIVERSITY A
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Table 6.1.1. Catch range during the
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Baltic herring trawling, Bothnian B
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6.1.3 Major international framework
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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 114 and 115: 112 Figure 6.5.1. Integrated classi
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 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
Page 164 and 165: 162 Baden, S., Boström, C. (2001).
Page 166 and 167: 164 Season 2001-2002. Acta Zoologic
Page 168 and 169: 166 Gasiūnaitė, Z.R., Cardoso, A.
Page 170 and 171: 168 HELCOM & OSPAR (2003): Joint HE
Page 172 and 173: 170 ICES (2008c). Report of the Bal
Page 174 and 175: 172 area: density-dependent effects
Page 176 and 177: 174 Noer, H., Clausager, I., Asferg
Page 178 and 179: 176 Scheffer M., Carpenter S.R., Fo
Page 180 and 181: 178 by passive acoustic monitoring.
Page 182 and 183: 180 Warzaw, Poland Vilhunen, Jarmo,
Page 184 and 185: 182 6.7 Alien speices Authors: Lepp
Page 186 and 187: ANNEX III: CONSERVATION STATUS OF T
Page 188 and 189: ANNEX IV: HABITAT OR SPECIES DISTRI
Page 190: ANNEX V: STATUS OF BREEDING AND WIN
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