L11 - Plankton and productivity Flashcards
Marine microbial food webs - DOM?
Dissolved organic matter
Marine microbial food webs - POM?
Particulate organic matter
Marine microbial food webs - Phycosphere?
Outside of cells where bacteria and the algal cell interact.
Marine microbial food webs - Saprotrophy?
Obtains nutrients from decaying matter (where fungi grow)
What are the different types of Plankton?
Phytoplankton, zooplankton, bacterioplankton, virioplankton (virus), mycoplankton (fungi).
What is Autotrophy?
Self nourishment (e.g. photosynthetic)
What is Heterotrophy?
Other nourishment (organic matter, other plants or animals)
What is Mixotrophy?
Mixed nourishment (both)
What is Holoplankton?
Entire drifter, entire life cycle spent floating e.g. phytoplankton, krill, copepods, formanifera.
What is Meroplankton?
Partial drifter, part of life cycle spent floating e.g. larval stage of sea urchin, lobsters etc is floating
Plankton come in a wide range of sizes such as?
Phytoplankton ranging over several orders of magnitude. Pico - 0.2 -> 2 microns, nano 2 -> 20, micro 20 - 200 microns (can see some of the largest - 0.2mm). What cyanobacteria is common in english channel covered by coccoliths cyanococcus emiliania huxleyi.
What are phytoplankton?
Mainly photoautotrophs. Eukaryotic, prokaryotic, diatoms, cyanobacteria, dinoflagellates, coccolithophores. Some hetero or mixotrophic. Eukaruotic cells are broken down into many different groups. Prokaryotic algae are cyanobacteria (only phytoplankton).
Eukaryotes vs Prokaryotes?
Prokaryotes
- DNA dispersed within cell
- Photosynthetic lamellae occur freely in the cytoplasm
- Cyanobacteria are bacteria where the thylakoid membranes are within the cytoplasm (classified as phytoplankton)
Eukaryotes
- DNA localised within a nucleus; essentially similar to those of higher plants
- Photosynthetic lamellae are confined within membranes as well defined chloroplasts
What are zooplankton?
Heterotrophs, invertebrates (normally <2mm long). Microzooplankton (20-200 um sized grazers), Mesozooplankton (meso = middle-sized; 02 - 20mm) (e.g. copepods). Macrozooplankton. Meroplankton - mero - greek for part (of the life cycle). Holoplanktonic - holo - greek for whole (of life cycle). The most important types of zooplankton include the foraminifera, radiolarians, cnidarians, cnidarians, crustaceans, chordates and mollsucs. Also dinoflagellates (if they are heterotrophic, otherwise they are phytoplankton) and ciliates.
What are the zooplankton groups?
Formanifera and Radiolarians. In phylum Retaria part of the supergroup Rhizaria. Dinoflagellates & Ciliates are in Alveolata. Cnidarians, crustaceans, molluscs (invertebrates) and chordates are all animals (metazoans)
Where are formaniferan species used in?
Dating rocks, due to their rapid evolution different stratigraphic layers can be mapped in fine detail.
What are Radiolarians?
Single celled protistans which absorb silicon from the surroundings and produce an exoskeleton. Prey is engulfed by pseudopods. Radiolarians have a mineral silicate test. 0.1-0.2mm. Have pseudopods for catching prey as with the Foraminiferans (forams). Sediments in ocean floor have a record of different species adapted to different temperatures.
What are Cnidarians?
Jellyfish, hydroids, sea anemones, corals. Some of these drifting animals (zooplankton)
What are copepods?
(Oar feet), mesozooplankton (mostly copepods), 10 orders of copepods (marine and freshwater) and have a larval form - they are small, abundant crustaceans.
What are the ten stages of copepods growth - with nauplii stages?
Eggs, then the nauplius stage (first stage), there are 5 or 6 nauplii stages: just a head and tail with thorax and abdomen absent. Then typically 6 copepodite stages
How are copepods important in biogeochemical cycles?
Copepods graze on phytoplankton and microzooplankton. Some eat organic detritus and the bacteria growing on it. Copepods are important for the conversion of PON to DON. Faecal pellets sink through euphotic zone, pellets circulate here and some sink to deep ocean.
What are Microzooplankton?
20-200um. Ciliates, dinoflagellates and formaniferans (single-celled). As well as small metazoans (multi-celled), such as copepod nauplii and some copepodites, and some meroplanktonic larvae. Major consumers of primary production as intermediaries between primary producers and copepods and as key components of the microbial loop.
Who is eating what? Micro vs Meso Grazing?
Picos - 97% micro, 3% meso
Diatom - 53% micro, 47% meso
Other - 59% micro, 41% meso
What are picophytoplankton?
Prochlorococcus (cyanobacteria)
Synechococcus (ditto)
Picoeukaryotic phytoplankton
Pelagomonas calceolata/Pelagococcus (Heterokonts)
Larger : Prymnesiophyte (Coccolithophore)
Dinoflagellates
Diatoms
Production: by phytoplankton
Picoplankton grazed mostly by the microzooplankton. Larger phytoplankton grazed mostly by the larger meso-grazing group (e.g. copepods).
What is mixotrophy?
Some autotrophs especially dinoflagellates are mixotrophic. Constitutive mixotrophs (possess their own chloroplasts) or non constitutive mixotrophs (use chloroplasts taken from their prey for phototrophy). Mixotrophy is poorly understood but is important in terms of carbon cycling (to what extent is mixotrophy contributing to primary production). Need to know the extent of mixotrophy to fully understand the potential of oceans to absorb carbon.
How important are mixotrophs?
A few decades ago, phytoplankton/zooplankton had a clear boundary with little mixotrophy thought to be going on. Now we know that many phytoplankton are often mixotrophic (e.g. Prymnesiophytes, Eustigmatophytes) and half the single-celled zooplankton are mixoplankton (e.g. Ciliates, dinoflagellates). Have plastids or algal endosymbionts.
What are the different climate regions of the ocean?
Temperate, subtropical and tropical regions. Different weather systems, geochemical regimes, heat and light levels. Different amounts of nutrients in these oceanic regions. Together this causes the phytoplankton and zooplankton profiles to differ.
What is GPP?
Gross primary production, refers to the total rate of organic carbon production by autotrophs.
What is Respiration?
Refers to the energy-yielding oxidation of organic carbon back to carbon dioxide
What is NPP?
Is GPP minus the autotrophs, own rate of respiration equivalent to the rate at which phytoplankton produces biomass.
What is SP?
Secondary Production, refers to the growth rate of heterotrophic biomass (bacteria, zooplankton, etc). SP is smaller than NPP. SP/NPP ratio is the efficiency in which organic matter is transferred to the food webs - fisheries depend on this for instance.
What is NEP?
Net ecosystem production is GPP minus all the respiration in the system (autotrophic + heterotrophic). NEP is also defined by the ecosystem boundaries. So for the euphotic zone: it is export of POC sinking into the ocean. Much of this is respired by heterotrophs on the way down (to DIC) so the export for the entire ocean into the sediments is less.
How do subtropical regions behave?
Less nutrient supply due to weather conditions. Small phytoplankton, grazed by microplankton. Fast nutrient turnover with low net export. Low nutrient supply, efficient recycling.
How do temperate regions behave?
More nutrients resuspension so rapid supply leads to large phytoplankton. These are predated by large zooplankton (e.g. copepods). Greater sinking due to larger sizes, faecal pellets, aggregates. High nutrient supply, inefficient recycling.
How are algae viewed from space?
Ocean chlorophyll content viewed from space. Composite satellite image. Intense red and green regions of high chlorophyll and upwelling of nutrients. Subtropical regions are nutrient poor, dominated by picoplankton.
Using satellites to determine annual production - Top chlorophyll concentration?
Phytoplankton productivity indicated by chlorophyll levels. Higher in summer months of temperate North and South. Driven by nutrient supply and light availability and warmer temperatures.
Using satellites to determine annual production - Bottom Nutrient (nitrate) concentration?
Nutrient upwelling indicated by raised nitrate levels in winter months of temperate North and South. Seasonality in temperate versus subtropical (oligotrophic waters).
What is Stratification?
Prevents nutrient exchange, caused by high gradients in temperature, salinity and density. Temperature is the main factor, salinity is local. Increased by surface temperature, glacial meltwater. Decreased by winds (mixing).
What are nutrient upwelling processes?
Brings nutrients to the surface. Driven by wind, Coriolis effect & Ekman transport or ocean floor topography.
What has algal blooms in the south west of england?
Emiliania huxleyi
What can you use to view blooms?
Satellite
Temperate waters : Seasonal cycling?
Winter (Jan/Feb) nutrients high due to storm mixing. Light increases are followed by temperature increases which causes. Stratification : warm water sits on top trapping nutrients. Light increase triggers the spring bloom in phytoplankton. Followed by a zooplankton peak. Phytoplankton gets grazed down leading both populations to fall. Upsurge of autumn nutrients leads to a smaller peak (fall mini-bloom). Peak smaller due to declining light and temperature.
What do microbial interactions affect?
Carbon productivity and export. Measurements supply the data for computational models. Testing in culture can verify hypotheses and reveal regulatory mechanisms. Models can provide further hypotheses for testing in the field.
