Plankton Behaviour Sinking Buoyancy And Vertical Migration

Cell size has a significant impact on the ability of phytoplankton cells to maintain their position at depths with adequate light and nutrients to sustain growth. In general, an increase in cell size results in an increase in sinking rate - with dead cells sinking at faster rates than live cells. Large phyto-plankton cells (such as diatoms) are disadvantaged by being highly susceptible to sinking, and may require strong vertical mixing (for example, caused by upwelling or strong winds) to...

Small And Irregular Zooplankton

The small, irregular zooplankton remaining in a 200 m mesh plankton sample are part of a very diverse group, and are of immense importance for the food web. Some comparatively large phytoplankton (less than 0.1 mm) will often be caught up in your sample, but fortunately they are quite distinctive (diatoms, and the dinoflagellate Ceratium, Figure 8.8A). Other single-celled animals include various star-shaped radiolarians and beautifully shaped foraminifera (the forams, Figure 8.8B). Radiolarians...

Analysis Of Phytoplankton Samples

Phytoplankton samples collected using appropriate quantitative sampling methods can be analysed in the laboratory by various counting methods or by the measurement of chlorophyll-a concentrations within the samples (Box 4.5). The chlorophyll-a concentration will provide an estimate of the standing crop or abundance of phytoplankton present in a water sample, but it will not provide any information on the composition of the phytoplankton present. To do this, you will need to identify and count...

What Are Plankton And Why Study Them

The term plankton refers to any small biota (from microns to centimetres) living in the water and drifting at the mercy of currents - ranging from bacteria to jellyfish. This definition is rather loose, as we often include jellyfish and krill (euphausids - and their larval forms) as plankton, yet they are active swimmers and are therefore technically referred to as 'nekton'. Sometimes even good swimmers, such as late-stage fish larvae are incorrectly termed 'planktonic', as they often show up...

Fixation and preservation of plankton

A fixative, such as formaldehyde, chemically treats the tissues stopping biochemical activity and increases the mechanical strength. A preservative, such as alcohol or salt, is a natural compound that reduces or stops decomposition without chemically fixing the tissue. Samples preserved in alcohol may shrink or become distorted more than in formaldehyde, but are safer and more pleasant to study, and are suitable for DNA analysis. Therefore the type and amount of fixative preservative used...

Jellyfish And Their Relatives

The jellyfish, or medusae, are treated separately here as they are increasingly common, and of great interest to humans because of their sting and as a fishery. Jellyfish belong to Phylum Cnidaria, which is divided into three classes Hydrozoa, Scyphozoa, and Cubozoa a fourth class of cnidarians contains all the benthic anemones and corals . They are distinguished from all other gelatinous zooplankton, and often from each other, by their stinging cells cnidocytes, nematocysts, Ostman 2000 . More...

Freshwater Zooplankton As Integrators And Indicators Of Water Quality

Monitoring and assessment of the freshwater environment are often based on turbidity, pH, dissolved oxygen, biological oxygen demand and nutrients. Point measurements of these physio-chemical traits can vary over hours to weeks, and from metres to kilometres, whereas we need traits that integrate the small scale variation. Zooplankton have been used widely as indicators to monitor and assess various forms of pollution including acidification, eutrophication, pesticide pollution and algal...