Human Footprint on the Seafloor
Brussel - RBINS 2/9/2011
Changes in macrobenthos: past
versus present
Jean-Sébastien Houziaux
BMM - UGMM
Human Footprint on the Seafloor
Brussel - RBINS 2/9/2011
New European legislation: what is a “Good Ecosystem
State”? GES
•
Since the 1990s, various european Directives aimed at nature protection
have been issued. The most recent is the « Marine Strategy » Framework
Directive – « MSFD »
•
The MSFD targets reaching a GES in European seas. Targets are defined
for 11 different descriptors of the marine ecosystem, including « seafloor
integrity ».
– “Sea-floor integrity is at a level that ensures that the structure and
functions of the ecosystems are safeguarded and benthic ecosystems,
in particular, are not adversely affected.”
•
This directive and others involves the definition of objective criteria towards
measurement of the GES
•
The measurement of the amplitude of change induced by human pressures
is necessary to set meaningful targets => Baseline assessment
=> Benthos composition = sensitive indicator for change in the seafloor
condition => Monitoring
Human Footprint on the Seafloor
Brussel - RBINS 2/9/2011
Belgium: a unique historical macrobenthic data set:
The surveys and material of G. Gilson, 1899-1908
Gilson’s
« ground-collector »
Gilson’s dredge
(Tow : one nautical mile)
Human Footprint on the Seafloor
Brussel - RBINS 2/9/2011
Seafloor and benthos, 1900: highlights
Western coast:
moderate diversity
and density (in- and
epifauna)
Epibenthic community
of open-sea gravels:
large taxonomic
diversity and densities
Highest densities
(infauna), low species
diversity
Human Footprint on the Seafloor
Brussel - RBINS 2/9/2011
Coastal waters: case of dominant bivalves
•
Long-term analysis challenges for coastal
macrobenthos:
Gilson’s dredge data Ù Recent Van Veen
data, 1994-2008 (joint DB of U. Gent + ILVOFisheries)
2°30
⇒ Sampling gear incompatibility:
Point sampling Ù towed dredge (1,9 km
long)
Different efficiencies
51°30
⇒ Different spatial distributions
⇒ Historic data on soft-bottom
macrobenthos: polychaetes not robust yet
Solutions:
– Spatial analysis of numerically dominant
bivalves through data gridding
51°10
– Standardize abundances to maximum
values => distribution of relative
densities
– P/A data => difference maps
3°30
Walchere
n
NL
Westerschelde
estuary
51°20
•
3°
F
Human Footprint on the Seafloor
Brussel - RBINS 2/9/2011
Coastal waters: case of dominant bivalves
General figures
45
1899-1914
1994-2008
Station occupancy rate (%)
40
Station occupancy rates
35
30
25
20
15
10
5
M
ys
el
la
bi
de
nt
at
a
A
br
a
M
al
ac
ba
om
a
ba
lth
ic
Te
a
lli
na
t
e
Te
nu
lli
is
Ve
na
ne
py
ru
g
pi
m
s
ae
se
a
ne
ga
le
ns
Te
is
lli
na
fa
bu
la
Te
lli
En
m
ya
si
s
fe
rr
ug
in
os
a
un
ca
ta
vi
tta
tu
s
su
bt
r
Sp
is
u
la
el
lip
tic
a
D
on
ax
a
so
lid
a
Sp
is
ul
100%
90%
Contribution to total
abundance
Proportion of total abundance
Sp
is
ul
a
M
ac
tr
a
st
ul
to
r
um
0
80%
Tellimya ferruginosa
Ensis directus
Tellina tenuis
70%
Tellina pygmaea
Tellina fabula
60%
Venerupis senegalensis
Mactra stultorum
50%
Macoma balthica
Spisula elliptica
Spisula solida
40%
Mysella bidentata
Donax vittatus
30%
Spisula subtruncata
Abra alba
20%
10%
0%
1899-1914
1994-2008
Human Footprint on the Seafloor
Brussel - RBINS 2/9/2011
Coastal waters: case of dominant bivalves
Geographic spreading
Muddy fine sand
⇒
Probable impact of change in fine
sediment dynamics (increased
turbidity?)
⇒
Probable effect of eutrophication /
pollution: increased benthic
biomass/productivity?
species:
Expansion
BUT:
(+ shifts in relative
density distribution)
-
Hydro-climatic factors (unlikely)
-
Ensis directus invasion (unlikely)
Other factors (fishery effects)?…
Shallow clean fine sand, filter- feeding species:
Change 1900 – 1970 > Change 1970-2000s
Regression
=> More ‘sophisticated’ biodiversity
analyses once polychaete data
checked
Macoma balthica (estuarine):
=> Incorporation of recent data from
Expansion from Schelde
Dutch waters
mouth to the entire coastal
waters
Human Footprint on the Seafloor
Brussel - RBINS 2/9/2011
Westerschelde mouth : 1900 versus 1980-82 (J.
Craeymeersch, IMARES)
100%
Venerupis
Phaxas
Nucula nitidosa
Mya arenaria
Ensis siliqua var_ minor
Ensis
Chamelea gallina
Cerastoderma edule
Angulus tenuis
Tellina tenuis
Fabulina fabula
Aequipecten opercularis
Tellimya ferruginosa
Striarca lactea
Barnea candida
Modiolus modiolus
Spisula elliptica
Spisula solida
Petricola pholadiformis
Mactra stultorum
Mytilus edulis
Donax vittatus
Macoma balthica
Abra alba
Mysella bidentata
Spisula subtruncata
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
1900_RA%
1980_RA%
Station occupancy (% stations - spreading)
45.00
40.00
35.00
30.00
25.00
20.00
15.00
10.00
5.00
0.00
Sp
isu
la
My sub
t
se
lla runca
bi d
t
en a
tat
Ma
Ab
a
co
r
ma a alb
a
b
Do
na althic
xv
a
My
itta
tilu
tus
M
Pe
tric actra s ed
ola
stu ulis
l
ph
ola torum
dif
Sp
o
rm
isu
is
la
Sp
Mo isula solid
a
di o
el l
ipt
lus
ica
m
Ba
rne odio
lus
ac
Str
an
Te
llim iarca dida
Ae
ya
qu
lac
fer
ipe
rug tea
cte
ino
no
sa
pe
Fa
rcu
bu
l ar
lin
i
s
af
ab
Te
ula
llin
at
An
en
Ce
gu
uis
ras
lus
t od
ten
erm
ui s
Ch
ae
am
du
el e
le
ag
En
all
sis
i
n
sili
a
qu
En
av
sis
ar _
mi
My
no
aa
r
Nu
ren
cu
a
ria
la
ni t
ido
sa
Ph
ax
a
Ve
s
ne
rup
is
Contribution to total density (14 species)
1900_F%
1980_F%
Human Footprint on the Seafloor
Brussel - RBINS 2/9/2011
Present-day observation
• Ecosystem engineering – Rabaut and coll.
– Lanice conchilega (tube building segmented worm)
• Essential structuring component of the “Abra alba” macrobenthic
community
– Owenia fusiformis (tube building segmented worm)
• Sand bank stabilisation. Recently thriving
• And in the 1900s and 1970s? => Gilson data and literature
Human Footprint on the Seafloor
Brussel - RBINS 2/9/2011
Coastal ‘ecosystem engineers’ in the past
L. conchilega
• 1900: occasional - widespread
• 1970: occasional
• 1980s: common, max densities
2000/m²
• 1990s-2000s: essential
component of A. alba
community – very large
densities (max 10,000/m² =>
“reefs”)
•
O. fusiformis
• 1900: occasional, offshore
• 1970: occasional, offshore
• 1980s: occasional, low densities
• Mid-2000s: strong expansion in
muddy fine sands with locally
very large densities (max
11,000/m² => “reefs”)
(NB. Typical component of
sandy gravel associated fauna
too)
=> Recent thriving
Human Footprint on the Seafloor
Brussel - RBINS 2/9/2011
Conclusions
• Macrobenthic communities of coastal waters since the 1970s are
altered compared to the early 1900s, with different species
thriving from the local pool.
• Increased influence of background turbidity (i.e. increased
chronic deposition of mud)?
• Relatively more species contribute substantially to bivalve
biomass: suggestion of biomass increase?
• Findings are consistent with moderate levels of organic
enrichment in highly mixed coastal waters (eutrophisation effect)
• “Ecosystem engineer” tube-building worms: fate in the long run,
link with ecosystem disturbance?
Human Footprint on the Seafloor
Brussel - RBINS 2/9/2011
Thank you for your attention !