Tule Ponds at Tyson
PHYTOPLANKTON
 

The organisms that live in pond  water are part of the invisible world that nourishes the ecosystem.  Plankton consists of two components: phytoplankton and the zooplankton.  Phytoplankton include photosynthetic floaters in the water column.  Since phytoplankton require light they are usually found only where light can penetrate.  Usually light can penetrate throughout the water column in a small pond, but this depends on the turbidity of the ponds.   Zooplankton includes representatives from protist as well as many invertebrates.  Many invertebrates like arthropods and mollusks have a larval stage which is spent as plankton.   

Together these microorganisms are important because they provide food for many of the larger organisms of the pond.  Zooplankton  consume other zooplankton and phytoplankton. Fish consume phytoplankton and zooplankton.

Microscopic algae  or phytoplankton come in a variety of shapes and in varied colors due to their different photosynthetic pigments. Algae can be unicellular and microscopic or colonial forming plate-like colonies, thread-like filaments, net-like tubes, or hollow balls.

DIATOMS
Identified by Ray Wong

Cyclotella sp.
Centric diatom. Planktonic (floater)
Family Coscinodiscaceae.
White scale bar is 5 microns

Cells usually solitary, but sometimes united to short chains. Valves circular, strongly to weakly undulate, undulations more evident in the middle area. Middle area punctuate, marginal area striate. Valve disc divided into two portions, the exterior annular, with striae smooth (costae) or punctuate, more or less fine, sometimes intermixed with small spines; always without a pseudo-nodule; center often bullate, smooth or granular, with granules sparse or radiating.

Melosira (Melosira sp.)
Centric diatom. Planktonic (floater)
Family Coscinodiscaceae.
White scale bar is 5 microns

Cells closely united to more straight; beadlike chains in the middle of the valve faces. Frustules globose, elliptical or cylindrical. Valves circular, often deeply convex and possessing a deep valve mantle, often with "small teeth" or short spines at the unction of the frustules, which are united into a filament. Valve surface either simple punctate or punctate and areolate; punctate usually in radiating lines or fascicules, often somewhat irregularly scattered in the center.

Gomphonema (Gomphonema sp)
Family Gomphonemateceae.
White scale bar is 5 microns

Cells usually in fan-shaped colonies, attached to dichotomously branched mucous stripes, sometimes free. Valves symmetrical on the apical axis, asymmetrical on the transapical axis. Valves naviculoid, more or less elongated, clavate or cuneate. Apical nodules small, axial area narrow, central area usually small, rounded. Raphe distinct, straight. Valve surface striate, striae punctate, transverse or slightly radiate. Girdle cuneate, simple. Connecting zone not complex, broader in the upper end than the lower end. Valve with a more or less distinct eccentric single central puncta.

Synedra(Synedra sp.)
Family Fragillariaceae.
White scale bar is 5 microns

Cells free or united into ribbon-like or gan-like clustered star-like colonies. Frustules linear, linear-lanceolate to very narrow lanceolate; apical axis is occupied by the pseudoraphe.Valves surface usually with transpical rows of deliate puncta and narrower pseudoraphe or wide lanceolate, hyaline area sometimes with scattered puncta.Lateral longitudinal ribs may be present in some forms. 

Surirella (Surirella sp.)
Family Surirellaceae.
White scale bar is 5 microns

Cells solitary, frustules in girdle view cuneate. Valves ovate, cuneate, reniform, elliptical or linear. Asymmetrical on the trans-apical axis, upper end usually broadly rounded, lower end cuneate or sub-acute. Valve surface costate, costae either short, or lengthened so that they meet at a median line in the apical axis. Central space often called the pseudoraphe, linear, lanceolate, often obscure, sometime hyaline or bearing faint folds or striae. Generally a bottom and littoral form, occasionally occurring as plankton. 

Cymbella (Calidris mauri)
Family Cymbellaceae.
White scale bar is 5 microns

Valve asymmetrical to the apical axis. Dorsal margin convex, ventral margin more or less straight; convex or concave. Axial area nearer the ventral margin in most species; central area with or without punctae.

Tabellaria (Tabellaria sp.)
Family Tabellariaceae.
 White scale bar is 5 microns

Cells quandrangular forming zigzag or straight filaments. Valves linear or oblong, inflated in the middle and at the apices. Rectangular in girdleview. Intercalary bands and septa present. In girdle view, the septa appear as short thickened lines. In valve view the septa extend at varying lengths under the surface of the valves. Valve finely striated, striae transverse, costae absent. Pseduoraphe narrow.

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