Marine Ecology

Plankton

I. Plankton- wanders

II. Size almost all are small

Table 2.1

Femtoplankton viruses 0.02-0.2 um

Picoplankton bacteria (heterotrophic and photosynthetic)

0.2- 2.0 um

Nanoplankton small phytoplankton 2-20 um

Microplankton phytoplankton, zooplankton 20-200 um

Mesoplankton phytoplankton, large zooplankton 0.2-20 mm

Macroplankton jellyfishes, … 2-20 cm

Megaplankton jellyfishes, … 20-200 cm

Why are most so small? Mineral nutrient absorption

Reduction of sinking rate

Reduction of predation

III. Phytoplankton

A. Photosynthesis 6CO₂ + 6H₂O à C₆H₁₂O₆ + 6O₂

1. Necessary resources carbon dioxide, water, light, chlorophyll, nutrients

2. Limitations

a. Light availability

Latitude, season, time of day, suspended matter, ice, clouds

Too little compensation light intensity

Too much inhibition

b. Mineral nutrient availability

With depth

With geography

Latitude

water depth

upwelling currents

terrestrial inputs

Nitrogen

Iron

Phosphorus

Other elements

Silicon

c. Predation (grazing)

d. Dilution of population

B. Productivity

gC/m² /unit of time (usually day or year)

cal/m² /unit of time

gross primary productivity – respiration = net primary productivity

GPP – R = NPP

Measurement

1. Oxygen production/ unit of time = NPP

BOD bottle and short incubation

final oxygen –initial oxygen = NPP

Respiration measured in an opaque bottle

Initial oxygen – final oxygen = R

2. Carbon 14

add a known amount of radioactive ¹⁴C as HCO₃

incubate in a BOD bottle for some hours and

then collect particulate matter on a filter

measure radioactivity with a scintillation counter

3. chlorophyll a

a. extract from water sample and measure with a spectrophotometer

b. measure specific wavelength of reflectance from Chl a from a satellite

4. dilution

geographic distribution

C. Phytoplankton taxa

1. cyanophyta (photosynthetic bacteria)

prokaryotes very small picoplankton to microplankton

Prochlorococcus sp. Picoplankton perhaps the world’s most numerous organism

Often secrete mucus coating and toxic or distasteful chemical

Therefore, not eaten as readily by zooplankton

Some are nitrogen fixers

2. diatoms

eukaryotes small to large microplankton to mesoplankton

silica shells (frustules) fit like lid and bottom of a shoe box

spiny to discourage predation

a few produce toxic chemicals

motile by pseudopodia

buoyancy enhanced by a lipid vacuole

3. dinoflagellates

eukaryotes small nanoplankton to microplankton

some have cellulose case

two flagella for motility

many produce toxic or distasteful chemicals

red tide, shellfish poisoning, Pfiesteria piscisida

D. dispersion and dominance

Patchy at all scales

Blooms common among net phytoplankton

More constant populations of picoplankton

Dominance of taxa varies with

temperature, salinity, nutrient concentration, season, depth, etc.

E. abundance of net phytoplankton

Low nutrient subtropical gyres (e.g. Sargasso Sea) 1000-10,000 cells/L

Inshore coastal (neritic) waters 100,000 – 900,000 cells /L

Estuary millions of cells/L

Gunston Cove billions of cells/L

IV. Zooplankton

A. Heterotrophic

most are herbivorous, some are carnivorous, some are feed on bacteria

B. Size

Nanoplankton (2 u) to megaplankton (200 cm)

C. Taxa and abundance

Protozoa

Flagellates, ciliates, forams, radiolarians, amoebas, etc.

feed on bacteria and phytoplankton

Copepods most diverse and most abundant of the net zooplankton

Larval stages: nauplius (1-6), copepodites (1-5)

Euphausids second most abundant

Shrimp-like,

Mysids

Cladocerans

Amphipods

jellyfishes

ctenophores

chaetognaths

rotifers

urochordata

salps (thaliaceans), appendicularians (larvaceans)

larvae of benthic invertebrates

larvae of fishes

D. copepod feeding

E. microbial loop

F. vertical migration

G. zooplankton consumers

fishes

larvae and juveniles of most, if not all, species

adults of herrings and anchovies and other, less abundant species

benthic suspension feeders

sea turtles

sea birds (penguins, etc)

whales, seals