Common aquatic proxies
Structural material
Silicates
Carbonates
Group
diatoms
chrysophytes
sponges
radiolaria
foraminifera*
ostracodes
*agglutinated forams have clastic, not carbonate tests
Diatoms
Unicellular, eukaryotic,
generally photosynthetic
microorganisms encased in a
cell wall impregnated with
silica. They tolerate a wide
range of thermal, pH and
salinity conditions in aquatic
habitats and wetland soils.
photo: Yuki Sawai
Centric and pennate diatoms
2
2
1
3
2
1
1. Valve face
2. Mantle
3. Girdle
(bands = cingula)
3
Diatoms
(major groups based on cell
morphology and ornamentation)
Eucentric - circular valve outline; radially symmetrical valve
ornamentation.
Eccentric - bipolar or multipolar outline; radial symmetry.
Araphid - bilateral symmetry to a central thickening (sternum).
Monoraphid - bilateral symmetry ; sternum has fissure (raphe) on one
valve only.
Naviculoid - bilateral symmetry; sternum has raphe on both valves.
Cymbelloid - raphes on both valves; assymetric on either the
longitudinal or transverse axis.
Nitzschoid - raphes on both valves raised above valve on keel.
Surirelloid - raphes on both valves raised above valve on wing.
Epithemoid - raphes on both valves within a canal.
Eucentric diatoms
valve view
Thalassiosira
Aulacoseira lacustris
Araphid (e.g.
“Fragilaria”)
and
monoraphid diatoms
(e.g. Cocconeis)
Epivalve (with raphe)
Hypovalve ( no raphe)
Naviculoid diatoms
Pinnularia abaujensis
Diploneis finnica
Frustulia rhomboides
Cymbelloid diatoms
Cymbella affinis
Eunotioid diatoms
Eunotia formica
Nitschzoid diatoms
keel
Epithemoid diatoms
canal
Surirelloid
diatoms
www.marbot.gu.se/files/melissa/checklist/diatoms.html#list
Diatoms: taxonomic problems
(e.g. freshwater and brackish Fragilariaceae)
Krammer & Lange-Bertalot
(1991)
Asterionella
Centronella
Ceratoneis
Diatoma
Fragilaria
Meridion
Opephora
Synedra
Tetracyclus
Tabellaria
Round, Crawford & Mann
(1990)
Asterionella
Centronella
Ceratoneis
Diatoma
Hannea
Meridion
Tabellariaceae
Fragilaria
Fragilariforma
Pseudostaurosira
Punctastriata
Staurosira
Staurosirella
Opephora(*marine)
Martyana
Ctenophora
Neosynedra
Synedra
Tabularia
Image in
light
microscope
a
b
d
SEM images
a) Fragilariforma
b) Staurosirella
c) Punctastriata
d) Staurosira
e) Pseudostaurosira
“Fragilaria”
morphology
c
e
From: Round et al. (1990) The
Diatoms. Cambridge U.P.
Diatoms: taxonomic problems synonymies
In Great Lakes catalogue
(www.umich.edu/~phytolab/
Great lakes/DiatomHomePage)
as Oestrupia zachariasi
In California Academy of
Sciences catalogue
(www.calacademy.org/research
/diatoms)
as Oestrupia bicontracta
Examples of applications of diatoms in
palaeoenvironmental studies
Sea-level change:
western Scotland
Palaeoseismology:
Discovery Bay, WA
Palaeolimnology:
depth: Lake Oloiden, Kenya
pH: Baby Lake, Ontario
temperature: Längsee, Austria
Diatom
record
of sea-level
change
in an isolation
basin on the
west coast of
Scotland
Discovery
Bay, WA
Diatom record
of tsunami
inundation of
marshes
Lake Oloiden, Kenya
(planktonic
centric)
(salt-tolerant
benthic, naviculoid)
Diatom-inferred pH change, Baby
Lake, Ontario (1870-1990)
pH
5
6
7
from: Dixit et al. (1992) Water , Air and Soil Pollution, 62, 75-87.
Late-Glacial summer surface water
temperature, Längsee (548 m asl), Austria
Pollen
Diatoms
Surface
Water Temp
from: Schmidt et al. (1998) Aquatic Sciences, 60, 56-88.
Chrysophytes
Although it is difficult
to distinguish species in
LM, the resting spores
of Chrysophytes may
prove useful as
supplementary sources
of environmental
information in
freshwater habitats.
Chrysophyte stomatocyst
(resting spore)
Freshwater sponges
(e.g. Heteromyenia sp.?)
1
2
1. sponge spicules and diatoms
(Stump Lake, BC)
2. gemmosclere
3. mega and microscleres
3
Sponge palaeofaunas, 20 ka BP - PD
(Jackson Pond, KY)
*
* H. latitientia now restricted to northern New England
Rhizoplegma
borealia
Radiolarians
• marine unicellular protists;
Lophospyris
pentagona
Lamprocyclas
maritalis
source: www. radiolaria.org
• siliceous skeletons in soft
cytoplasm; lipid globules in
cytoplasm (and spines?) enhance
buoyancy;
• planktonic: occur from surface to
depths of several hundred
meters;
• size range = 2 - 30 mm diameter;
• families distinguished by skeletal
shapes; some groups are solitary,
others colonial;
• species abundance related to
water temp., salinity, and nutrient
status.
An example of the
application of
radiolarians in
palaeooceanographic
studies
Core 1019
from: Pisias et al (2001)
Quat. Sci Rev., 20, 1561-1576
Radiolarian assemblages in the Pacific Ocean
Max. factor loadings
from:
Pisias et al.
(2001)
Quat. Sci
Rev., 20,
1561-1576.
Radiolarian assemblages in core 1019
(989 m water depth)
YD
green line = GISP2 d18O record; black line=radiolarian record
Foraminifera
Foraminifera are single-celled protists that live in all
marine environments. They inhabit the sea floor
(benthonic forms) or the surface layer of the oceans
(planktonic forms). Most of the soft tissue of the cell
of a foraminifer is enclosed within a test which may be
composed of secreted organic compounds and mineral
grains cemented together (agglutinated test), or
secreted calcite or aragonite (calcareous test). The
calcareous tests are divided, in part, into hyaline and
porcellaneous types based on the orientation of the
calcium carbonate crystallites comprising the test.
Examples of (1) agglutinated and
(2) calcareous foraminifers
(1) Textularia forquata
(2) Elphidium excavatum
length = 0.18 mm; breadth = 0.09 mm
max. diam. = 0.48 mm; thickness = 0.20 mm
foram photos and info. from http://www.cs.uwindsor.ca/meta-index/fossils/woop.html
“N. pachy left”
Examples of
applications of
foraminifera in
palaeoenvironmental
studies: coiling and
ocean temperature
from: Rohling et al. (1998) Nature, 394, 162-165.
Forams: “aplanktic” episodes in the
Red Sea confirm eustatic lowstands
Low RSL = hypersaline Red Sea = no planktonic forams
Palaeo-temperature, core DSDP-609
(N. Atlantic) based on “%N. pachy left”
100%
0%
Bensonocythere americana
dorsal view
lateral view
length = 0.69 mm
height = 0.38 mm
width = 0.35 mm
Ostracodes
Ostracodes are crustaceans with two
calcareous valves hinged along the
dorsal margin to form a carapace which
is commonly ovate or kidney-shaped.
They have adapted to marine
environments — oceans, estuaries and
lagoons; hypersaline environments;
freshwater environments — lakes,
ponds, rivers and springs; and
terrestrial environments such as the
moist humus of forests. The majority
of ostracodes are benthonic in habit.
source: www.cs.uwindsor.ca/metaindex/fossils/woop.html
Applications of ostracodes in Quaternary
palaeoenvironmental research:
Lake Manitoba during the Holocene
Salinity
(g/L)
1 2 3 4
Applications of
ostracodes:
changes in depth ranges
(controlled by water
temperature)
record oceanographic
conditions on Bahama
Bank
pores
Krithe sp.
from: Rodriguez-Lazaro & Cronin
(1999) Palaeo3, 152, 339-364.
4°
cooler
2°
cooler
Aquatic proxies as sources of proxy data:
advantages
• short generation times; quick response to
environmental change
• many groups cosmopolitan (cf. regional floras and
megafaunas)
• in situ, not derived from surrounding terrestrial
habitats, therefore representative of conditions
within the water body, rather than the
watershed.
Aquatic proxies as sources of proxy data:
limitations
• no ‘parent’ for reference material (cf. pollen & spores)
• species concept often difficult to apply;
• small forms hard to distinguish in LM;
• unstable taxonomies; many synonyms;
• meagre ecological information;
• often responsive to a wide variety of inter-linked
environmental stimuli (water temperature,
conductivity, pH, nutrient status, depth);
• small size leads to homogenization by currents, etc.
(i.e. allochthonous components common in fossil
assemblages).