Common aquatic proxies

diatomschrysophytesspongesradiolariaforaminifera*ostracodes

Silicates

Carbonates

Structural material Group

*agglutinated forams have clastic, not carbonate tests

Diatoms

photo: Yuki Sawai

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.

Centric and pennate diatoms

1. Valve face2. Mantle3. Girdle

(bands = cingula)

1

1

2

2

3

2

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 onevalve 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

colony in girdle view

valve view

Thalassiosira Aulacoseira lacustris

Araphid (e.g. “Fragilaria”)

and monoraphid diatoms

(e.g. Cocconeis)

Epivalve (with raphe) Hypovalve ( no raphe)

Naviculoid diatomsPinnularia abaujensis

Diploneis finnica Frustulia rhomboides

Cymbelloid diatoms

Cymbella affinis

Eunotioid diatomsEunotia formica

Nitschzoid diatomskeel

Epithemoid diatoms

canal

Surirelloid diatoms

www.marbot.gu.se/files/melissa/checklist/diatoms.html#list

Diatoms: taxonomic problems(e.g. freshwater and brackish

Fragilariaceae)

AsterionellaCentronellaCeratoneisDiatomaHanneaMeridion

AsterionellaCentronellaCeratoneisDiatomaFragilariaMeridionOpephoraSynedraTetracyclusTabellaria

Krammer & Lange-Bertalot(1991)

Round, Crawford & Mann (1990)

FragilariaFragilariformaPseudostaurosiraPunctastriataStaurosiraStaurosirellaOpephora(*marine)MartyanaCtenophoraNeosynedraSynedraTabulariaTabellariaceae

“Fragilaria”

morphology

Image in light microscope

SEM imagesa) Fragilariformab) Staurosirellac) Punctastriatad) Staurosirae) Pseudostaurosira

a

d

c

e

b

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, Ontariotemperature: Längsee, Austria

Diatom record

of sea-levelchange

in an isolationbasin on thewest coast of

Scotland

DiscoveryBay, 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)

from: Dixit et al. (1992) Water , Air and Soil Pollution, 62, 75-87.

pH

5 6 7

Late-Glacial summer surface water temperature, Längsee (548 m asl),

AustriaPollen Diatoms Surface Water Temp

from: Schmidt et al. (1998) Aquatic Sciences, 60, 56-88.

Chrysophytes

Chrysophyte stomatocyst(resting spore)

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.

Freshwater sponges

(e.g. Heteromyenia sp.?)1. sponge spicules and diatoms (Stump Lake, BC)2. gemmosclere3. mega and microscleres1

2 3

Sponge palaeofaunas, 20 ka BP - PD

(Jackson Pond, KY)

* H. latitientia now restricted to northern New England

*

Radiolarians

Lamprocyclasmaritalis

Lophospyrispentagona

Rhizoplegmaborealia

• marine unicellular protists;• 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.

source: www. radiolaria.org

An example of the application of radiolarians in

palaeo-oceanographic

studies

from: Pisias et al (2001) Quat. Sci Rev., 20, 1561-1576

Core 1019

Radiolarian assemblages in the Pacific Ocean

Max. factor loadings

from: Pisias et al.(2001) Quat. SciRev., 20, 1561-1576.

Radiolarian assemblages in core 1019 (989 m water depth)

green line = GISP2 18O record; black line=radiolarian record

T1YD

ForaminiferaForaminifera 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

(2) Elphidium excavatum(1) Textularia forquata

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

Examples of applications of foraminifera in

palaeoenvironmental studies: coiling

and ocean temperature

“N. pachy left”

Forams: “aplanktic” episodes in the Red Sea confirm eustatic

lowstands

Low RSL = hypersaline Red Sea = no planktonic forams

from

: R

ohlin

g e

t al. (

1998)

Natu

re,

394,

162-1

65.

Palaeo-temperature, core DSDP-609(N. Atlantic) based on “%N. pachy

left”

100%

0%

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.

length = 0.69 mmheight = 0.38 mm  width = 0.35 mm

source: www.cs.uwindsor.ca/meta-index/fossils/woop.html

Bensonocythere americana

dorsal view

lateral view

Applications of ostracodes in Quaternary palaeoenvironmental research:

Lake Manitoba during the Holocene

from

: C

urr

y (

19

97

) C

an. J. E

art

h S

ci., 3

4, 6

99

-70

8.

1 2 3 4

Salinity(g/L)

Applications of ostracodes:

changes in depth ranges (controlled by water temperature)

record oceanographicconditions on Bahama

Bank

Krithe sp.

pores

4°cooler

2°cooler

from: Rodriguez-Lazaro & Cronin (1999) Palaeo3, 152, 339-364.

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).