Benthos. Mats Westerbom

1.

Benthos
Mats Westerbom
Coastal Ecology I
Paloma Lucena-Moya
2020-2021

2.

Benthos
From Ancient Greek
βένθος (bénthos, “the
depths”).
Benthos is the community
of organisms that live on,
in, or near the benthic zone
(seabed or seafloor).
Mats Westerbom

3.

BENTHOS
Substratum
Rocky
Feeding
Size
Macro
(>0.5 mm)
Soft
sediments
Meio
(0.1-0.5 mm)
Micro
(<0.1mm)
Habitat/Site
Epifauna
Infauna
Filter
Type
Deposit
Zoo
(benthos)
Phyto
(benthos)

4.

ZOOBENTHOS
PHYTOBENTHOS
Macrozoobenthos
Marine macroalgae
Meiozoobenthos
Microphytobenthos (benthic microalgae)

5.

6.

BENTHOS
Substratum
Rocky
Feeding
Size
Macro
(>0.5 mm)
Soft
sediments
Meio
(0.1-0.5 mm)
Micro
(<0.1mm)
Habitat/Site
Epifauna
Infauna
Filter
Type
Deposit
Zoo
(benthos)
Phyto
(benthos)

7.

Benthic fauna (invertebrates): How big are you?
Three different size classes:
1. Macrobenthos / Macrofauna > 0.5 mm (but also > 1 mm)
Polychaetes (Polychaeta)
Eunice pennata
Fredrik Pleijel.
Amphipods (Amphipoda)
Gammarellus angulosus
Snails (Gastropoda)
Hydrobia acuta

8.

Benthic fauna (invertebrates): How big are you?
Three different size classes:
2. Meiofauna / Meiobenthos 0.1 – 0.5 mm
Ostracoda
Foraminifera
Nematodes
© Peter Serov
“Temporary meiofauna e.g., juvenile/larvae stages of macrofauna eg. Polychaetes”

9.

Benthic fauna (invertebrates): How big are you?
Three different size classes:
3. Microfauna / microbenthos < 0.1 mm
Protists and bacteria
Euglena sp.

10.

BENTHOS
Substratum
Rocky
Feeding
Size
Macro
(>0.5 mm)
Soft
sediments
Meio
(0.1-0.5 mm)
Micro
(<0.1mm)
Habitat/Site
Epifauna
Infauna
Filter
Type
Deposit
Zoo
(benthos)
Phyto
(benthos)

11.

What do you (benthic invertebrate fauna) feed?
Herbivores: feed on plant material
Sea urchin (Paracentrotus lividus)
Carnivores/ predators: feed on live individuals of various sizes
Saduria entomon
Detritivores: feeds on detritus (breaks down dead plant or animal matter)

12.

How do you feed?
Suspension feeders
Feed on the plankton above
They have special structures designed to capture
and concentrate particulate matter and
phytoplankton.
They dominate areas where turbulence is greater
and the substrate is composed of larger sand grains.
(e.g., bivalves, ophiuroids, crinoids),
Filter-feeders find their food in much the same way as suspension-feeders: the only difference is that they
themselves create water currents towards the special food retention appendages by means of siphons or
articulated appendages.

13.

How do you feed?
Deposit feeders
Eat organic material in sediments
They burrow below the surface and extract food from large
amounts of sediment.
Turbulence is low and the substrate consists of fine, silt
particles and detritus (dead organic mater).
(e.g., holothurians, echinoids, gastropods),
Marenzelleria viridis

14.

Baltic clam Macoma balthica
An illustration of the two ways of feeding by the Baltic clam, Macoma balthica
(© Anna Törnroos)

15.

BENTHOS
Substratum
Rocky
Feeding
Size
Macro
(>0.5 mm)
Soft
sediments
Meio
(0.1-0.5 mm)
Micro
(<0.1mm)
Habitat/Site
Epifauna
Infauna
Filter
Type
Deposit
Zoo
(benthos)
Phyto
(benthos)

16.

17.

The major part of the benthic fauna is buried in the sediments and is,
thus, called “infauna“
Profile of the sea floor showing typical
infaunal/epifauna organisms (from Pierre Tardent).
a)
b)
c)
d)
e)
f)
g)
h)
i)
k)
l)
m)
Barnacles (Balaniden)
Blue mussels (Mytilus edulis)
Polychaete Lanice conchilega,
Polychaete Lagis koreni,
Snail Littorina littorea,
Rasor clam (Ensis americanus),
Bivalve Cerastoderma edule,
Bivalve Scrobicularia plana,
Bivalve Mya arenaria
Polychaet Arenicola marina,
Polychaete Hediste diversicolor,
Bivalve Macoma balthica

18.

BENTHOS
Substratum
Rocky
Feeding
Size
Macro
(>0.5 mm)
Soft
sediments
Meio
(0.1-0.5 mm)
Micro
(<0.1mm)
Habitat/Site
Epifauna
Infauna
Filter
Type
Deposit
Zoo
(benthos)
Phyto
(benthos)

19.

Environmental (abiotic) facors
affecting life:
Rocky bottoms
M. Westerbom
M. Westerbom
Soft bottoms

20.

Soft
sediments

21.

http://faculty.chemeketa.edu/afrank1/rocks/sedimentary/sedtexture.htm

22.

Finland 2016

23.

24.

Storfjärden
”Mud”, which can be anything (from silt to
clay and everything mixed with organic
matter)
Fine-grained soft bottom, with a high % of
organic material (OM) and a high water
content

25.

26.

The successive degradation of organic matter (OM) in the

27.

ENV-317 Meribiologia
…and
brown.
Seafloor…flat,
brown
Notnot
justjust
flat…
and therefore unimportant ?
Biologically and functionally diverse
Soft bottoms

28.

Soft sediments:
• Largest ecosystem of the world´s seafloor (70%)
• 3-D living environment (biotic interactions): Biodiversity and complexity
• Secret-garden: microphytobenthos, organic matter
• Sediment-seawater interface is permeable: fluxes (O2, nutrients)
• Macrofauna: Foundation for food webs and ecological functioning
D. Lohrer
macrofauna
Microphytobenthos (secret garden)
Bioturbation: macrofauna reworking of seafloor can oxygenate (i.e. expose anoxic sediments to oxic seawater) and regulate
nutrient fluxes (A. Villnäs-07.02.20): think on earth-worms and compost.

29.

Baltic seagrass meadow: Zostera marina
Mediterranean: Posidonia oceanica

30.

Baltic: High diversity of aquatic plants (mixed seagrass)
Perfoliate pondweed, Potamogeton perfoliatus
Sago pondweed, Stuckenia pectinata
Sea lace, Chorda filum
Eurasian water milfoil,
Myriophyllum spicatum
Filamentous drift algae
Beaked tasselweed, Ruppia marina
Spiral ditchgrass, Zannichellia major
Image credit: Alf Norkko

31.

The rocky intertidal is a challenging habitat
Physical stress factors include:
• UV light
• waves effect
• high fluctuation in temperature
• dehydration
• salinity
Biotic interactions, especially competition and predation, are more important in
the lower parts of the tidal zone (more diverse).
Supratidal zone
Mostly
shelled
organisms
Many
soft organisms
and algae
Subtidal
Intertidal zone
Littorina-gastropods
Fucus spiralis
F. vesiculosus
F. serratus

32.

Rocky shore-Baltic Sea (no tides)
In the littoral, life on the shore is complicated with water fluctuations and winter.
There are ephemeral filamentous algae (temporal, opportunistic, turf algae).
In the upper part of the sublittoral, there is a monospecific bladder wrack-zone (Fucus
vesiculosus), with a variety of algal and animal communities. Below the red agal zone
and the blue mussel reef
depth
Turf algae
Cladophora glomerata
Filamentous agal
zone
LITTORAL
INFRALITTORAL
Macroalgal zone
Fucus vesiculosus
Red algae
Mussel zone
Furcellaria lumbricalis
Photos: M. Westerbom
Mytilus trossulus x edulis

33.

Blue mussels dominate S Finland rocky reefs
3m
8m
15m
Photos: Mats Westerbom

34.

M. Westerbom
Baltic Sea macroalgae: underwater forests
Total 442 macroalgal species observed (Takolander et al. 2017 J. Sea Research_http://dx.doi.org/10.1016/j.seares.2017.03.007)
Fucoids most important habitat-forming species in Baltic Proper
F. vesiculosus is the main habitat-forming species (90% biomass, perennial)
Filamentous algae are major seasonal primary producers (summer peaks)
Eutrophication has caused extensive blooms of filamentous algae, and declines in abundance and depth
penetration of fucoids (light, oxygen)
• Algal detritus: organic material – connectivity (deep areas) – food – carbon sink?

35.

Fucoids in the Baltic: salinity controlled species
M. Westerbom

36.

ENV-317 Meribiologia
Blue mussel reefs
Mats Westerbom
Dominate the benthic animal biomass
Few meters to 30 m (or too muddy)
Increases habitat complexity (biodiversity)
Filter feeder: excretion feeds algae and benthic
macrofauna + faecal deposits (microbial degradation)
• Key role in the coastal food-web
Mats Westerbom

37.

ENV-317 Meribiologia
Seagrass meadow (SG)
Baltic example: benthic habitats
Fucus-bed (FV)
Blue mussel reef (BM)
Attard et al. 2019 Limnology & Oceanography Letters
Rodil et al. 2019. Ecosystems
Bare sand (BS)
https://doi.org/10.1002/lol2.10107
https://doi.org/10.1007/s10021-019-00427-0
Mixed macrophyte (MM)

38.

BELOW THE SURFACE Dive into the Baltic Sea with the
fieldworkers of the NANNUT-project
LINK to watch the video!
Assignment 3: Please answer these questions after watching the video
1. What factors determine the type of habitat?
2. What major types of habitats are mentioned?
3. What are their characteristics?
4. What are the threats to these habitats?
5. Why are they important?
Deadline: 12.10.20 (23:00 Helsinki) Upload in Moodle