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Marine Ecology - Airoldi > 10 Biogenic Reefs > Flashcards

10 Biogenic Reefs Flashcards

1
Q

what are biogenic reefs?

A
  • a habitat is a structure or setting e.g. rocky reefs, sedimentary bottoms…
    (can be occupied by certain plants or animals)
  • marine habitats generated by the presence of organisms such as:

sea grass beds
kelp forests
oyster reefs
coral reefs

  • including foundation species/ ecosystem engineers
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2
Q

What are foundation species/ ecosystem engineers?

A
  • Species that generate whole habitats
  • They often increase species diversity
  • often facilitate the presence of numerous associated species by reducing environmental stress, and offering shelter and food
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3
Q

What are coral reefs?

A

Coral reefs are marine ridges or mounds, which have formed over millennia as a result of the deposition of calcium carbonate by
- living organisms, predominantly corals

  • but also a rich diversity of other organisms such as coralline algae and shellfish
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4
Q

distribution of cold water and tropical coral reefs

A
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5
Q

What is Lophelia?

A
  • a cold-water coral which grows in the deep waters throughout the North Atlantic ocean and can form extensive reefs
  • example for coral of temperate mesotrophic coral reefs
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6
Q

mesotrophic habitats

A
  • Oceanic waters with low light penetration (where less than 1% of light penetrates, approximately between 50 and 200 m depth)
  • Corals, algae, and other organisms adapted to the low light conditions originate Marine Mesophotic Biogenic Habitats (MBHs)
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7
Q

the bathymetric zonation patterns incoral reefs are quite distinct. how?

A
  • there is a transition from the light-dependent zooxanthellate corals to azooxanthellate scleractinian corals and sponges
  • a transition from fleshy seaweeds to encrusting red algae
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8
Q

what are coralligenous reefs?

A
  • unique hard bottom biogenic formations
  • in the Mediterranean
  • mainly produced by the accumulation of calcareous encrusting algae
  • that grow in dim light conditions
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9
Q

distribution of coralligenous reefs in the mediterranean

A
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10
Q

coralligenous formations

A
  • banks
  • rims
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11
Q

what is a bank? (coralligenous formations)

A
  • Banks are flat frameworks with a variable thickness that ranges from 0.5 to several (3–4) m
  • mainly built over more or less horizontal substrata
  • have a very cavernous structure that often leads to a typical morphology
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12
Q

what are rims? (coralligenous formations)

A
  • Rims develop in the outer part of marine caves and on vertical cliffs
  • usually in shallower waters than banks
  • The thickness of rims is also variable and ranges from 20–25 cm to >2 m; thickness increases from shallow to deep waters
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13
Q

what is the dominant flora in coralligeneous reefs?

A
  • main red algal building species
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14
Q

what is the dominant fauna

A

1) Fauna contributing to buildup from algae: bryozoans, polychaets, corals and sponges
2) Cryptofauna: colonizes small holes
3) Epifauna & Endofauna: living over or inside the buildup
4) eroding species

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15
Q

name some animal building species in coralligenous reefs

A

(A) Miniacina miniacea (B) Pentapora fascialis (C) Myriapora truncata (D) Serpula vermicularis (E) Leptopsammia
pruvoti

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16
Q

name some bioeroders incoralligenous reefs

A

A) Cliona viridis
(B) Sphaerechinus granularis
(C) Echinus melo
(D) browsing marks of Sphaerechinus granularis over Lithophyllum frondosum.

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17
Q

spatial interactions in coralligenous assemblages

A
  • crucial in the buildup of coralligenous assemblages
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18
Q

are predators in coralligenous assemblages specialized?

A
  • yes
  • strong prey selection in coralligenous communities
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19
Q

Disturbances in coralligenous assemblages

A
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20
Q

what is the ecological role of marine animal forests?

A
  • 3D habitat forming species
  • nursery and refuge
  • benthic-pelagic coupling
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21
Q

why are marine animal forests highly threatend?
(name disturbances)

A
  • climate change
  • pollution
  • mechanical damages
  • over-exploitation of resources
  • non-indigenous species
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22
Q

what are maerl beds?

A
  • maerl is a collective term of several species of calcified red seaweed
    (e.g. Phymatolithon calcareum, Lithothamnion glaciale, Lithothamnion corallioides and Lithophyllum fasciculatum)
  • they live unattached on sediments
  • can form extensive beds in favorable conditions (typically 30% cover or more)
  • mostly in coarse clean sediments of gravels and clean sands or muddy mixed sediments
  • Maerl beds have been recorded from a variety of depths, ranging from the lower shore to 30m depth
  • maerl requires light to photosynthesize, depth is determined by water turbidity
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23
Q

what are Ecosystem Services Provided by Bivalve Shellfish?

A
  • regulating
  • provisioning
  • supportive
  • cultural
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24
Q

table of ecosystem services provided by oyster reef habitat

A
25
Q

what can oyster reefs function as? why?

A
  • as shoreline stabilizer
  • because they are structures that interact with tidal and wave energy
    (just like engineered shoreline stabilization devices by baffling waves and increasing sedimentation rates)
26
Q

table of annual value of ecosystem services provided by oyster reefs (2011)

A
27
Q

types of shellfish habitats

A
  • reefs
  • beds
  • aggregations
28
Q

reefs (as type of shellfish habitats)

A
  • provide the dominant structural component of the benthos
  • significant vertical relief (≥ 0.5 m) through their accumulated physical structure.

-Examples include the eastern oyster (Crassostrea virginica), Pacific oyster (Crassostrea gigas).

29
Q

beds (as type of shellfish habitats)

A

provide the major structural habitat component of the benthos
- occur at high densities and form macro-relief (< 0.5m) on otherwise unstructured bottom.

  • Examples include Olympia oyster (Ostrea conchaphila), ribbed mussel (Geukensia demissa), horse mussel (Modiolus modiolus), green mussel (Perna viridis), European flat oyster (Ostrea edulis), Chilean oyster (Tiostrea chilensis).
30
Q

aggregations (as type of shellfish habitats)

A
  • form secondary structure on top of other underlying hard substrate or physical features (e.g., rocky intertidal, mangrove roots and rhizomes)

Examples include pen shells (Pinna spp., Atrina spp.), giant clams (Tridacna gigantica), mangrove oyster (Crassostrea rhizophorae, C. brasiliana, and C. gasar), Sydney rock oyster (Saccostrea commercialis), crested oyster (Ostreola equestris), slipper cupped oyster (Crassostrea iredalei)

31
Q

what did oyster reefs use to dominate?

A
  • Oyster Reefs used to dominate Temperate Estuaries: From China to Chesapeake
  • now: many losses and issues
32
Q

what was the First Global Assessment (“Shellfish reefs at Risk”) aiming for?

A
  • aiming to improve the condition of reef forming bivalve populations
  • raising awareness
  • enhance conservation
  • enhance restoration
  • improve management
33
Q

map of oyster reefs at risk

A
  • 85% loss of oyster reef ecosystems in bays and ecoregions
  • mangrove and saltmarsh (~50%)
  • coral reef (~20%)
34
Q

facts about Ostrea edulis (flat European oyster)

A
35
Q

native distribution range of Ostrea edulis

A
36
Q

harvesting history of Ostrea edulis

A
37
Q

native oyster landings

A

(Anlandungen von einheimischen Austern)

38
Q

historical losses of oysters. what are the most likely drivers?

A
  • Estimated average losses > 90% up to virtual extinction at a number of localities
  • Most likely drivers of loss: overfishing, outbreaks of diseases, habitat transformation, adverse environmental conditions and non-native competitors and parasites
39
Q

consequences of the loss of native oyster beds (example at the wadden sea)

A
  • In the Wadden sea the loss of biogenic habitats, mainly Ostrea edulis beds and seagrasses, indicated as the cause of extinction of 26 species during the past 2000 years
40
Q

what about the current oyster beds?

A
  • they are severely depleted
  • they are debated to what extent current fragmented patches of wild oyster habitats could owe their survival to inputs of larvae from cultivated oysters
41
Q

harvesting of oysters

A
  • can lead to extinction
  • Intensive harvesting until 1994
  • subsequent collapse
  • harvesting ceased in 1999
  • From >1000 tonnes of harvest annually to a point where it is now difficult to find just 60 individual oysters with a dredge (Virvilis and Angelidis 2006)
42
Q

Aquaculture and oysters

A
  • Aquaculture now provides the main supply of native oysters in most European countries (probably sustaining some natural populations)
  • Industry seriously affected by epidemic diseases
  • The introduced Pacific oyster Crassostrea gigas now provides the major share of oyster production in Europe
42
Q

what was O. edulis also affected by?

A
  • pests and diseases
43
Q

Magallana gigas (pacific oyster)

A
  • Introduced for oyster farming
  • very rapid expansion
  • now widely common in the wild outside the influence of marine farming
  • ultimate driver of local exctinction of O. edulis in some areas (e.g. Venice and Grado)?
44
Q

pacific oyster invasion in the wadden sea

A
45
Q

other threats for O. edulis

A
  • by-catch in trawl fisheries
  • poor water quality and pollution
  • changes to the environment (e.g., habitat loss due to coastal development),
  • the introduction of other non-native competitors, predators and diseases
46
Q

attempts to improve fishery of O. edulis

A
  • attempts date back to at least 17th century
  • Scientific studies on the biology and ecology of this species
  • Fisheries and acquaculture generally regulated at a regional to national level
  • EU, national and local legislation related to issues of water quality and spread of diseases
47
Q

protection of O. edulis was and is limited

A
  • “Reefs” including biogenic reefs are listed as a conservation feature of the Habitats Directive but no specific reference to O. edulis reefs
  • included in the Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR) list of threatened and/or declining species and habitats
  • included in the Red lists of some regions (e.g.,Wadden Sea, Black Sea)
  • designed as a named species in the UK Biodiversity Action Plan
  • Conservaton and restoration efforts restrained by a lack of awareness of poor conditions and risks of these habitats, which are perceived at lower risk of exctinction than other species and habitats
48
Q

opportunity for protecting O. edulis

A
  • protecting the remaining beds
  • assessing the distribution and condition (Need for better information on the distribution and status of O. edulis habitats in Europe)
49
Q

loss of O. edulis reef before discovery

A
50
Q

what is the O. edulis UK Biodiversity action plan?

A
51
Q

what about the potential of O. edulis restoration?

A
52
Q

what are the Conclusions for O. edulis?

A
53
Q

What are recommendations for O.edulis?

A
54
Q

Oyster reef restoration

A
  • Restoration or enhancement of populations of commercially exploited shellfish depressed by over-harvesting and/or reduced environmental quality remains the principal motivation behind most shellfish ‘restoration’ efforts.
  • Direct and indirect ecosystem services (e.g. filtering capacity, benthic–pelagic coupling, nutrient dynamics, sediment stabilization, provision of habitat, etc.) derived from oyster habitat have been largely ignored or underestimated.
  • Only recently, the restoration of lost ecological function associated with shellfish communities has been included in our discussions and related research examining habitat development and function through a scientific approach.
55
Q

potential for created oyster shell reefs as a sustainable shoreline protection (Strategy in Louisiana)

A

Establishment of fringing oyster shell reefs in coastal marsh environments is a particularly attractive shoreline stabilization method because it involves

1) the use of native materials
2) the potential for sustainability and possible growth over long temporal scales
3) the added value of contributing to overall ecosystem stability and quality through its habitat creation and water quality functions

oyster reefs are common inmany estuarine habitats –> their use as a shoreline protection tool would be convenient and relatively cheap, if a steady supply of shell exists.

56
Q

effects of fish production on oyster reefs

A
  • estimated enhancement of fish production resulting from restoring oyster reef habitat
57
Q

Unprecedented Restoration of a Native Oyster Metapopulation

A
  • Native oyster species were once vital ecosystem engineers
  • but: their populations have collapsed worldwide
  • because of overfishing and habitat destruction
  • In 2004, a vast (35- hectare) field experiment was initiated by constructing native oyster reefs of three types:
    1) high-relief
    2) low-relief
    3) and unrestored
    in nine protected sanctuaries throughout the Great Wicomico River in Virginia, United States
  • Upon sampling in 2007 and 2009, we found a thriving metapopulation comprising 185 million oysters of various age classes

–> Oyster density was fourfold greater on high-relief than on low-relief reefs, explaining the failure of past attempts.
–> Juvenile recruitment and reef accretion correlated with oyster density, facilitating reef development and population persistence.
- This reestablished metapopulation is the largest of any native oyster worldwide

–> validates ecological restoration of native oyster species.

Marine Ecology - Airoldi (15 decks)

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