Bio-processes

**189**

**Chapter 8**

**Abstract**

winter (12.5 mg.L<sup>−</sup><sup>1</sup>

**1. Introduction**

the microphytobenthic community.

microphytobenthos, system dynamic

radiation penetrates down to the bottom [2].

Subtropical Coastal Lagoon from

The chapter is about the study of environmental conditions and the structure of the benthic diatoms community in Peixe Lagoon, which is inserted in a National Park in southern Brazil. The study was carried out covering four seasons from 2011 to 2012. The system is shallow (<60 cm) located parallel to the coastline, and it is connected to the ocean through a single channel, which occurs naturally or through human action. In this lagoon, during the study, the water temperature ranged between 15.3 and 32.1°C, and the dissolved oxygen presented higher value in the

) and lower value in the summer (7.5 mg.L<sup>−</sup><sup>1</sup>

from mesotrophic to hypereutrophic conditions. The salinity varied between 1.3 and 36.2%, and these variations were mainly related to meteorological conditions. The community of diatoms in Peixe Lagoon is composed by 62 taxa distributed in 30 genera composed largely of marine, brackish, and few freshwater species. Among the attributes of the community, composition better reflects the environmental variations. The opening and closing of the channel, salinity, temperature, and the action and direction of the wind are variables influencing the dynamics of

The shallow coastal lagoons are low depth water column mixing systems in which phytoplankton and microphytobenthos communities, microscopic eukaryotic photosynthetic algae, and cyanobacteria which live on the seabed [1] play a key role in the primary production and recycling of matter and nutrients. The role of microphytobenthos is quite important where macrophytes are absent and light

Microphytobenthos are composed of a set of microorganisms distributed in very diversified taxonomic groups, among which the diatoms are an important and often dominant component in estuarine and shallow coastal environments. These algae have varied adaptive strategies for adhesion and migration on different substrates, and there is a very large number of species sensitive to environmental changes.

**Keywords:** environmental variables, diatoms, community attributes,

). The lagoon ranged

Southern Brazil: Environmental

Conditions and Phytobenthic

Community Structure

*Leticia Donadel and Lezilda Torgan*
