Phyto

ALGAE Introduction • a very diverse group of plants in the oceans & freshwater environments, but a few algae live on land • they range in size from tiny, microscopic forms, to a very complex forms such as seaweeds and kelps • algae include both prokaryotic and eukaryotic organisms (prokaryotic algae: Cyanobacteria and Prochlorophyta; range from unicells and colonies to the simplest of branched filaments) • they possess a variety of cellular structures with arrangement of cells to form plant bodies, and the pigments for photosynthesis

Ecological importance of algae • important primary producers in standing & running waters, thus provide the principal energy base for many aquatic food webs • play important biogeochemical roles in terms of nutrient fixation and spiraling within the ecosystem • macroalgae provide a breeding habitat and a refigium for various animals • shifts in species composition can affect feeding relationships, population growth, and guild structure at higher trophic levels in aquatic food webs

Algae and its role in carbon cycle in aquatic ecosystems

Algal bloom in eutrophic lake can cause detrimental effects to the ecosystem

The Primary Classification of Algae

The primary classification of algae is based on five main criteria: iii. Photosynthetic pigments iv. The nature of the food reserves v. The nature of cell wall components vi. The types of flagella vii. Certain details of cell structure

Division

Class

Rhodophyta (red algae)

Rhodophyceae

Chlorophyta (green algae)

Chlorophyceae Prasinophycea Charophyceae

Euglenophyta (Euglenoid)

Euglenophyceae

Chloromonadophyta (chloromonad)

Chloromonadophyceae

Xanthophyta (green-yellow algae)

Xanthophyceae

Bacillariophyta (diatom)

Bacillariophyceae

Chrysophyta (golden brown algae)

Chrysophyceae

Phaeophyta (brown algae)

Phaeophyceae

Pyrrophyta (dinoflagelum)

Dinophyceae Desmophyceae

Cryptophyta (crytomonad)

Cryptophyceae

Cyanophyta (blue-green algae)

Cyanophyceae

Phytoplankton (phyton = plant; planktos = wandering) Microscopic, free-floating algae that drift on the ocean & freshwater currents. These tiny plants, comprised of single cells, or chains of cells, form the basis for marine ecosystem They are characterized by size, shape, and pigmentation All phytoplankton have Chlorophyll a and accessory pigment that are either photosynthetic or photoprotective accessory pigments During photosynthesis, phytoplankton use solar radiation, water and carbon dioxide to yield glucose (a carbon form of energy they can utilize) and oxygen Phytoplankton and other plants use glucose as "building blocks" to grow. Also, through photosynthesis, these microscopic marine plants nourish the entire marine food web phytoplankton are essential because they are a critical part of the ocean biology and in part control the level of carbon dioxide in the atmosphere

Microspora sp

Gloeocapsa sp.

Synedra sp

Phytoplankton move by swimming or changing their density Sinking is slowed down by viscous drag on cell wall Gas vacuoles & gas vesicles in the cells increase floatation Buoyancy is regulated by: • synthesis of the gas vacuoles • increase in cell ballast • vacuole dilution due to growth • Flagella & cilia

Measurement Van Dorn sampler Small pumps driven by battery-powered motors Simple hand-pump vacuum siphoning systems Coring devices (sediments) Plankton nets We can observe phytoplankton with satellite instruments via ocean color remote sensing. The satellite detects different concentrations of Chlorophyll a with ocean color satellites.

Seasonal cycles of phytoplankton Spring bloom: • physical effect - increase of sunlight & solar heating • high growth rates occur only after thermal stratification Stratification: • cuts off the supply of nutrients from the hypolimnion – limit growth • Stratification within the euphotic layer is a primary factor controlling phytoplankton growth • two main factors limiting phytoplankton growth: illumination and nutrients • Light limitation is crucial under low stratification (e. g., winter convection), because algae cells are dispersed by turbulent mixing within deep dark layers • Nutrient limitation is crucial under enhanced stratification (e. g., seasonal thermocline in summer), because nutrients do not penetrate into the euphotic (i. e., well illuminated) upper mixed layer •

• The hydrometeorological factors (heat flux, wind, freshwater load with precipitation and river discharge) either increase or decrease the stratification within the euphotic layer • Typical seasonal cycles of phytoplankton result from the combined effect of seasonal cycles of hydrometeorological factors influencing water stratification within the euphotic layer. The most illustrative is the phytoplankton seasonal cycle in mid-latitudes with two maxima in spring and autumn: The rising T increase zooplankton grazing rates & microbial parasitic attacks

Season

Hydrometeorologica l factors

Stratification

Phytoplankton growth

Winter

Maximum cooling of

Deep convection

Winter minimum resulting from light limitation

upper layer Spring

Heating of upper layer increases

Summer

Maximum heating of upper layer; Minimum mixing

Formation of seasonal thermocline Maximum stratification

Spring bloom

Summer minimum resulting from nutrient limitation

Fall

Cooling of upper layer increases; mixing increases

Erosion of seasonal thermocline

Autumn bloom

Seasonal cycles of phytoplankton: driven by water temperature, stability, zooplankton abundance

the presence of a spring and fall phytoplankton bloom, followed by an abundance maximum of zooplankton. the tropical ocean generally lacks pronounced seasons, thus no pronounced seasonal cycle of plankton abundance and production.

Typical vertical profiles of phytoplankton biomass (chlorophyll), production, temperature, and nitrate concentrations in the tropical, oligotrophic ocean

Annual growth cycle is modified by: iii. Nutrient availability iv. The degree of thermal stratification v. Algal movement vi. Interalgal competition vii. Zooplankton grazing viii.Parasitism by protozoans, fungi, bacteria and viruses The dynamics features of aquatic water bodies – color, clarity, trophic state, water chemistry, the taste & odor of the water, animal plankton and fish production – depend to a large degree on phytoplankton

2. Periphyton • A periphyton mat is a community of many kinds of tiny organisms including algae, cyanobacteria, bacteria, insect larvae, and snails. • Periphyton is very productive (makes a lot of living material). • Periphyton provides shade in the marsh and protection for small fish and insects in the water column. • Periphyton stores nutrients and builds soil • attached algae, grow on submerged substrates (rocks, mud or vegetation) • pennate diatoms, filamentous greens, and blue-greens are common members of the periphyton • pennate diatoms and blue-greens – move over the substrates by gliding • filamentous greens are fixed • the entire thallus may be appressed to the substrates

Microflora

Substrate

Epilithic

Rocks

Epipelic

Muds or sediments

Epipsamic

Sand surfaces

Epiphytic

Plants or macroalgae

Epizoic

Animals

Epidendric

Wood

• availability of light and grazing by aquatic insect larvae and snails are important in regulating periphyton biomass • their colonization of new sites follows a pattern akin to that in terrestrial vegetation • attached algae follow the cycles of the material on which they grow • the type of substrate is important in determining whether a particular species is able to grow

2.a. Epilithic communities • Algae growing on rock surfaces • the algae are adapted to swiftly flowing water by being either encrusting or basally attached • four groups of algae are found frequently in the epilithic flora, Cyanophyta, Chlorophyta, Rhodophyta and encrusting Bacillariophyta

Green color on rock surfaces are due to the occurrence of algal mats (Cyanophyta, Chlorophyta), and brown color patches are dominated by Bacillariophyta

2.b. Epiphytic communities • algae growing on microscopic or macroscopic algae (seaweeds, Chara, Cladophora, etc.) and other aquatic plants (Bryophyta, Pteridophyta or Angiosperm) • the attachment of epiphytic algae is in part related to the structure of the surface layers of the plants

2.c. Epipsamic communities • algae growing on sand • mainly composed of diatoms, blue green algae, coccoid Chlorophyceae and Euglenoids

The advantages of using algae as biological indicators in monitoring and protecting aquatic environments: •

Algae generally have rapid reproduction rates & very short life cycles making them valuable indicators of short-term impacts • As primary producers, algae are most directly affected by physical and chemical factors • Sampling is easy, inexpensive & creates minimal impact to resident biota • Algal assemblages are sensitive to some pollutants, which may not visibly affect other aquatic assemblages • Relatively standard methods exist for evaluation of functional and non-taxonomic structural characteristics of algal communities • Algal cells accumulate and concentrate the pollutant substances • Similar species assemblages occur predictably at locations having comparable physical and chemical conditions • Algal assemblages are typically species rich • Algal community structure and function respond rapidly to changes in environmental conditions. Algae exhibit predictable responses to a variety of environmental stressors • Algal taxa vary considerably in their sensitivity to common pollutants • Pollution tolerance well documented