Freeliving nematode assemblages on European sandy beaches

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Free-living nematode assemblages on European
sandy beaches Tom Gheskiere, Magda Vincx
Steven Degraer
SeMBSS - Friday January 30th 2004
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• Why sandy beaches?
• definition
• it is considered to be a sandy littoral area
  open to the sea (excluding sandflats in estuaries
  or closed lagoons)
• dominate most of the temperate and tropical
  coastlines (Europa gt30)
• biological deserts ?? ? rocky coastlines
• high ecological (birds, feeding ground for
  fishes, ...) and economical (tourism, fisheries,
  bufferzones against the sea, ...) values
• simple ecosystem (waves, tides, sediment
  currents)
• principal ecological functions water filtration,
  mineralisation of organic matter
• dynamic interface between land and sea
  terrestrial ? marine gradients
• ecosystem strongly subjected to stress
  (pollution, tourism, euthrophication, ...)
• quite unknown infauna

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Sandy beach morphodynamics
DIMENSIONLESS FALL VELOCITY (Deans parameter O)
2
5
HW
0
LW
-2
HW
HW
0
0
LW
LW
0
100
200
-2
-2
HW
0
0
100
200
0
100
LW
-2
0
100
200
RELATIVE TIDAL RANGE (RTR)
low tide terrace
ultra-dissipative
HW
HW
HW
0
0
0
-2
-2
-2
LW
-4
-4
-4
-6
LW
LW
-6
200
0
100
300
200
100
0
300
low tide bar/rip
0
200
400
500
600
100
300
Transition to tide-dominated flats

• Hb modal breaker height
• Ws sediment fall velocity
• T modal wave period
• MSR Mean Springtide Range

Modified from Masselink Short, 1993 Short, 1996
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Why marine nematodes?
(Modified from J. Vanaverbeke)
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• Why marine nematodes?
• dominant in the marine meiofauna
• important in the small foodweb
  (Bacteria-Protista-Meiofauna)
• highly diverse phylum ( 4600 marine species)
• very resistant
• no escape from bad conditions
• everywhere in high abundances
• diverse tolerant ? sensitive
• trophic diverse
• high and constant reproduction
• longest surviving taxon
• extremely beautiful !!

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I. Nematode zonation patterns on a sandy beach

• Aims
• structural and functional diversity?
• nematode zonation patterns?
• relation with sediment?

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O 7.34 RTR 9.94
MHWS
Elevation (MLWS)
MLWS
50
100
150
200
250
300
350
400
450
Length (m)
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• Environmental characteristics
• silt, very fine sand, fine sand, medium sand,
  coarse sand, very coarse sand, gravel, shell
  fractions, sorting coefficient, skewness,
  kurtosis, TOM

S8
S3
S3
S8
S9
S9
S7
S7
S6
S5
S6
S4
S5
S4
S2
S2
S1
S1
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Meiofauna 14 higher meiofaunal taxa
Ind./10cm²
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Nematodes (1) species richness

• 88 species, 65 genera and 26 families
• 4 species new to science (!!) (Daptonema,
  Theristus, Dichromadora, Parachromadorita)

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Nematodes (2) Multivariate analyses
S9
S9
S1
S2
S8
S1
S8
S2
S8
S9
S1
S2
S7
S5
S6
S7
S4
S5
S5
S6
S4
S7
S6
S4
S3
S3
S3
Stress 0,08
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Nematodes (3) Community analyses
100
80
60
middle beach
Cumulative dominance ()
40
Cumulative dominance ()
20
0
1
10
100
Species rank
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Nematodes (3) Species lists
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Nematodes (4) Intertidal species plot (top 10
nematodes)
MT
MHWS
MLWN
MLWS
MHWN
Relative abundance ()
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Nematodes (5) Trophic diversity
Relative abundance ()
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I. Nematode zonation patterns on a sandy beach

• Conclusions
• Quite high and unknown diversity
• Highest density near MLWS, highest diversity on
  middle beach
• Nematode zonation exists, strongly correlated
  with sediment and tidal zonation patterns
• Non-selective deposit feeders dominate, except
  epistratum feeders in the driftline

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II. Nematodes from (non)touristic beaches

• Aim
• Comparison (species richness, taxonomic diversity
  dominance, community structure) of two sandy
  beaches with the same morphodynamics and sediment
  composition though with a different touristic
  impact

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Nematodes (1) species richness
74 species of free-living nematodes 7200
identications
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Nematodes (2) Multivariate analysis
Stress 0,13
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Nematodes (3) Taxonomic diversity
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Nematodes (3) Taxonomic diversity
upper and middle part of the Viareggio beach have
a significantly lower (plt0.05) taxonomic spread
than expected from the regional master nematode
list of 74 sp.
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Nematodes (4) Maturity Index
ANOVA, Plt0.01
2.76 0.12
1.96 0.11
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II. Nematodes from (un)disturbed sandy beaches

• Conclusions
• Beaches are clearly different species diversity
  and species dominance
• Beaches harbour different nematode communities
  especially on the upper beach
• There is a loss of taxonomic distinctive species
  on the upper beach, i.e. STRESS
• (According to the Maturity Index, the touristic
  beach has a lower ecological quality and can be
  considered as disturbed)

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