Biology and Ecology of the Benthic Algae

Abstract

This chapter describes the diversity of the microscopic and macroscopic benthic algal assemblages of the Bahía Blanca Estuary, including ecological aspects like their habitats, their role as primary producers, and the main interactions with other biota of the estuary. The microphytobenthic community is well developed in the soft sediments of the estuary. It is dominated by cyanobacteria and diatoms, which are key elements in the stabilization of sediments and nutrient cycling. They also interact with the macrobenthic fauna. On the other hand, the assemblages of macroscopic algae are poor in number of taxa. The majority of macroalgae are annual and opportunistic species, making use of the artificial substrate that is eventually available for their attachment. A few macroalgae are perennial mat-forming species, and there are also species considered exotic or introduced. Despite the fact that the little availability of hard substrate and the turbid waters limit the development of macroscopic algae, there are local species that flourish when conditions become favorable and produce blooms. These blooming species constitute promising candidates for their utilization in biomitigation. Although the benthic algae have been less studied than other biological groups, there is no doubt that these primary producers are vital components of this estuarial system.

Glossary

Amoeboid:

Type of cell organization that lacks a cell wall and the protoplasm undergoes frequent changes in shape.

Blade:

(= lamina) Flattened structure that is somewhat leaflike.

Bloom:

Massive or conspicuous growth of algae, usually a large percentage of the total cells belong to one or a few species.

Coccoid:

Simple cell type that is spherical, subspherical, or rod-shaped.

Cytokinesis:

The process by which one cell physically divides into two cells.

Epilithic:

Organisms living attached to the surfaces of rocks and stones.

Epipelic:

Organisms living attached to the surfaces of mud or sand.

Epiphytic:

Organisms living on the surfaces of plants or algae, using it for support but not for nutrition.

Epizoic:

Organisms living on the surfaces of animals.

Eukaryotic:

Organisms composed of cells with membrane-bounded nucleus. Most contain cells with a complex organization, with microtubules, membrane-bounded organelles, and chromatin organized into more than a single chromosome.

Eutrophic:

Waters that contain relatively high levels of dissolved nutrients (e.g., nitrate, phosphate); typically exhibit high levels of primary productivity.

Flagellum:

Long, threadlike organelle that projects out of the cell and functions in motility. In eukaryotic cells, they consist of a 9 doublet + 2 central singlet array of microtubules.

Frustule:

In diatoms, the silica cell wall or test, composed of two valves.

Holdfast:

A cell or multicellular structure that functions in attachment to a substrate.

Kelp:

Large phaeophytes that are members of the Laminariales.

Mastigonemate:

Stiff, lateral hairs borne by a flagellum, consisting of a base, a tubular shaft, and several terminal hairs.

Monophyletic:

Evolutionary term referring to a trait or group of organisms that evolved directly from a common ancestor.

Phagotrophic:

Mode of nutrition referring to heterotrophic protoctists or tissue cells that ingest solid food particles by phagocytosis.

Phycobiliproteins:

Complex of phycobilins with protein found in cyanobacteria, rhodophytes, glaucocystophytes, and some cryptophytes.

Phycobilisome:

Cellular structure containing phycobilin pigments and arranged as protrusions on the surface of the thylakoids of cyanobacteria, rhodophytes, and glaucocystophytes, but within the thylakoids (between membranous stacks) in the plastids of cryptophytes.

Photosynthetic pigments:

Pigments are chemical compounds present in algae by which the energy of sunlight is captured for photosynthesis.

Plastids:

Generic term for photosynthetic organelles present in algae. Plastids contain the enzymes and pigments for photosynthesis, ribosomes, and other structures.

Polyphyletic:

Evolutionary term referring to a trait or group of organisms that derived from more than one common evolutionary ancestor or ancestral group.

Prokaryotic:

Typically unicellular organism lacking a distinct nucleus and membrane-bound organelles.

Propagules:

Generative structure, any unicellular or multicellular, capable of survival, dissemination, and further growth.

Somatic:

General term referring to the body (soma) of an organism. The part not involved in reproduction or germination.

Spore:

Reproductive cell (motile or not) that originates by mitosis (mitospore) or meiosis (meiospore).

Stipe:

Stalk, stemlike portion of the algal thallus.

Symbiotic:

Physical association between organisms of different species.

Thallus:

The body of an alga that is not differentiated into roots, stalks, and leaves as in other plants.

Thylakoid:

Flat saclike structure formed by membranes that is present in the cytoplasm of cyanobacterial cells and in plastids of eukaryotic algae and plants.