**6.1 Spatial and temporal variation**

*Lagoon Environments Around the World - A Scientific Perspective*

and in the following months (**Figure 7**).

**5. Benthic diatoms composition**

(6.4 m/s). A sharp decrease occurred in February 2012 (4.6 m/s). The predominant direction of the wind in the fall was south and southwest, shifting northeast in July

The diatoms community in Peixe Lagoon is composed by 62 taxa distributed in 30 genera composed largely of marine, brackish, and few freshwater species (**Table 2**). Similar results were recorded in an area adjacent to this study [28], where

The genera with the greatest number of taxa are *Amphora* Ehrenberg ex Kützing,

*Nitzschia* Hassall, and *Diploneis* Ehrenberg ex Cleve. The freshwater species that probably tolerate the wide variation of salinity are *Amphora ectorii*, *Cocconeis neodiminuta*, *C. euglypta*, *Chamaepinnularia truncate*, *Diploneis aestuari*, *D. didyma*,

*Planothidium delicatulum*. More than 50% of taxa are cosmopolitan, and the remaining are restricted to a large extent to South America. An aspect to be highlighted is

*Distribution of the diatoms at the North—N, Center—C, and South—S in the four seasons of the year in Peixe* 

*Nitzschia palea*, *N. scalpelliformis*, *N. frustulum*, *N. vitrea* var. *salinarum*, and

a total of 73 predominantly benthic and brackish taxa were found.

**196**

**Table 2.**

*Lagoon, from June 2011 to February 2012.*

The community attributes (richness, diversity, and evenness) showed a decreasing spatial gradient from the North to the South stations. The specific diversity ranged between 2.3 bits/ind. at North and 0.4 bits/ind. at South and the evenness varied between 74 and 20% at North and South stations.

Seasonally, in fall, without connection with the ocean, the community attributes presented the highest values. After the channel opening, the richness was similar in winter and spring, rising in the summer. The values of evenness and diversity increased from winter (0.6–1.7 bits/ind.) to summer (0.8–2.3 bits/ind.) (**Figure 8**). However, these attributes did not differ significantly between the seasons and the station sampling.

## **6.2 Diatoms composition related to environmental variables**

The composition of the diatoms and the physical and chemical variables of the water in the canonical correspondence analysis (**Figure 9**) of the abundant species (25 species with more than 5% abundance) can better demonstrate the community dynamics in the system.

The sampling units of the South station are grouped on the negative side of axis 1. They were related to the lower values of conductivity and salinity. The species associated with this axis were *Cocconeis sawensis*, *Fragilaria eichhornii*, *Cocconeis euglypta*, *Fallacia florinae*, and *Halamphora coffeaeformis*. In this axis, it is also possible to observe the separation of the sampling units from the North, mainly due to the difference in temperature between hot and cold seasons, in fall and winter months. The related species were *Nitzschia scalpelliformis*, *Luticola simplex*, *Ehrenbergia granulosa*, *Rhopalodia runrichiae*, *Diploneis smithii*, and *D. didyma*. The sampling units of the Center station are grouped on the positive side of axis 2, where higher values of salinity and temperature were observed in the hotter seasons, as well as the lower values of silica and ORP. The species *Opephora pacifica*, *Catenula adhaerens*, and *Opephora* aff. *mutabilis* were related to this axis (**Figure 10**).

During the study, we observed periods with higher and lower marine influence, due to the opening of the channel. In fall, the only season in which the channel was closed, the composition of diatom species was distinct in the north and south of the lagoon. The south and south-west quadrant wind might also have been an influence factor for the distinction of community composition.

After the channel opening, it is possible to observe the difference in the composition of the community at the southern portion in relation to the north and center portions of the lagoon. The species highlighted in the south (*Cocconeis sawensis*, *C. euglypta*, *Fallacia florinae*, and *Halamphora coffeaeformis*) are found in brackish and marine waters, with the exception of *C. euglypta*, a characteristic species of freshwater, but it supports high conductivity water [64]. So, the marine influence appeared as one of the main factors affecting spatial diatom composition and spatial distribution in the lagoon.

#### **Figure 8.**

*(a–f) Distribution of community attributes related to sampling stations and the seasons of the year in Peixe Lagoon from June 2011 to February 2012.*

However, the salinity cannot be considered as the only driving force that determines the composition of diatom species in environments with marine influence in subtropical and temperate regions. Temperature is also considered a very important environmental factor [11]. In Peixe Lagoon, the temperature difference between hot seasons (spring and summer) and cold seasons (fall and winter) also differentiated

**199**

temperatures and salinities.

**Figure 9.**

**6.3 Diatoms related to sediment**

*strigosa (Semstr), Fragilaria eichhornii (Fraeic).*

usually associated with sand grains.

*Subtropical Coastal Lagoon from Southern Brazil: Environmental Conditions and Phytobenthic…*

the composition of the species. *Diploneis interrupta*, *D. didyma*, *D. smithii*,

*N. scalpelliformis*, and *Luticola simplex* were related to the colder seasons. This was also observed for species of *Diploneis* in the sediment of sublittoral zone of the Gulf of Trieste [65]. *Catenula adhaerens*, *Nitzschia frustulum*, *Opephora aff. mutabilis*, *O. pacifica*, and *Seminavis strigosa* were related to the sampling units with higher

*Canonical correspondence analysis (CCA) of the abundant species in the sampling stations and seasons fall, winter, spring, summer in Peixe Lagoon. For legends of the variables, see Table 2. Amphora ectorii (Ampect), A. maracaiboensis (Ampmar), Amphora sp.2 (Ampsp2), Catenula adhaerens (Catadh), Cocconeis euglypta (Coceug), C. sawensis (Cocsaw), Diploneis didyma (Dipdid), D. interrupta (Dipint), D. litoralis* 

*(Diplit), D. smithii (Dipsmi), Ehrenbergia granulosa (Ehrgra), Fallacia florinae (Falflo), F. subforcipata (Falsub), Halamphora coffeaeformis (Halcof), Luticula simplex (Lutsim), Navicula phylleptosomaformis (Navphy), Nitzschia frustulum (Nitfru), N. palea (Nitpal), N. scalpelliformis (Nitsca), Opephora aff. mutabilis (Opemut), O. pacifica (Opepac), Placoneis elegantula (Plaele), Rhopalodia runrichiae (Rhorun), Seminavis* 

Another important factor regarding diatom distribution is the sediment characteristic [66, 67]. In the Center and South stations, the surface of the Peixe Lagoon is essentially covered by sandy sediments, in which we find *Campylosira cymbelliformis*, *Catenula adhaerens*, *Dimeregramma minus*, and *Staurophora soodensis* species

In deeper sites of the lagoon, such as near the North, the sediments are thinner, with addition of silt and clay [49]. In this station, where muddy sand is present, we observed more clearly the seasonal variation of the diatom community. This site also showed highest diversity (1.7–2.4 bits/ind.) and richness (16–26 táxons) and the presence of more exclusive epipelic species; among these are the following: *Caloneis permagna*, *Luticola simplex*, *Nitzschia dissipatoides*, *N. scapelliformis*,

*DOI: http://dx.doi.org/10.5772/intechopen.87776*

*Subtropical Coastal Lagoon from Southern Brazil: Environmental Conditions and Phytobenthic… DOI: http://dx.doi.org/10.5772/intechopen.87776*

#### **Figure 9.**

*Lagoon Environments Around the World - A Scientific Perspective*

However, the salinity cannot be considered as the only driving force that determines the composition of diatom species in environments with marine influence in subtropical and temperate regions. Temperature is also considered a very important environmental factor [11]. In Peixe Lagoon, the temperature difference between hot seasons (spring and summer) and cold seasons (fall and winter) also differentiated

*(a–f) Distribution of community attributes related to sampling stations and the seasons of the year in Peixe* 

**198**

**Figure 8.**

*Lagoon from June 2011 to February 2012.*

*Canonical correspondence analysis (CCA) of the abundant species in the sampling stations and seasons fall, winter, spring, summer in Peixe Lagoon. For legends of the variables, see Table 2. Amphora ectorii (Ampect), A. maracaiboensis (Ampmar), Amphora sp.2 (Ampsp2), Catenula adhaerens (Catadh), Cocconeis euglypta (Coceug), C. sawensis (Cocsaw), Diploneis didyma (Dipdid), D. interrupta (Dipint), D. litoralis (Diplit), D. smithii (Dipsmi), Ehrenbergia granulosa (Ehrgra), Fallacia florinae (Falflo), F. subforcipata (Falsub), Halamphora coffeaeformis (Halcof), Luticula simplex (Lutsim), Navicula phylleptosomaformis (Navphy), Nitzschia frustulum (Nitfru), N. palea (Nitpal), N. scalpelliformis (Nitsca), Opephora aff. mutabilis (Opemut), O. pacifica (Opepac), Placoneis elegantula (Plaele), Rhopalodia runrichiae (Rhorun), Seminavis strigosa (Semstr), Fragilaria eichhornii (Fraeic).*

the composition of the species. *Diploneis interrupta*, *D. didyma*, *D. smithii*, *N. scalpelliformis*, and *Luticola simplex* were related to the colder seasons. This was also observed for species of *Diploneis* in the sediment of sublittoral zone of the Gulf of Trieste [65]. *Catenula adhaerens*, *Nitzschia frustulum*, *Opephora aff. mutabilis*, *O. pacifica*, and *Seminavis strigosa* were related to the sampling units with higher temperatures and salinities.
