DSpace Coleção:http://repositorio.ufc.br/handle/riufc/162024-03-28T22:07:34Z2024-03-28T22:07:34ZEcologia populacional do bivalve Isognomon bicolor (C.B. ADAMS, 1945) no litoral do semiárido brasileiroNunes, Luysa Maria de Souzahttp://repositorio.ufc.br/handle/riufc/745682023-10-04T13:01:29Z2022-01-01T00:00:00ZTítulo: Ecologia populacional do bivalve Isognomon bicolor (C.B. ADAMS, 1945) no litoral do semiárido brasileiro
Autor(es): Nunes, Luysa Maria de Souza
Abstract: Among marine ecosystems, coastal environments are one of the most
susceptible to biological invasion. When sessile bivalves invade these
ecosystems, they often form dense and extensive banks that reach a wide
spatial scale and can have serious impacts on ecosystem health. An example of a sessile bivalve that has spread along the entire Brazilian coast is Isognomon bicolor. In Brazil, this Caribbean bivalve was first recorded in 2002. Over these two decades, several population studies were carried out along the entire coast; however, none of these studies were able to observe these populations at different times of the invasion. Thus, to understand the processes involved in biological invasions, two populations of I. bicolor at different stages of invasion were monitored between July 2018 and July 2019. In chapter I, the spatial and temporal distribution of these populations was analyzed. In chapter II, the population structure and dynamics of these populations were compared. The results of Chapter I revealed that the populations of the invasive bivalve have significantly different population densities. The spatial and temporal distribution of the invasive bivalve also occurred differently between the populations studied, confirming our hypothesis that the populations of the invasive bivalve vary according to the time of invasion. This population variation is described in the literature as a phenomenon called “boom-bust”, where populations of invasive species go through a period of population expansion, which usually occurs at the beginning of the invasion, followed by a marked population decline. In Chapter II, the structure and dynamics of populations of I. bicolor confirm that the oldest populations of this invasive bivalve are composed of larger individuals and are maintained by the longevity of adults. Recent populations have smaller individuals in their composition and are supported by intensive recruitment that overcomes the high mortality rates present in the population. Knowing that the invasion process is highly dynamic, continuous and long-term monitoring of these populations is important in order to elucidate the processes involved in biological invasions such as the boom-bust. Thus, the prevention and mitigation of impacts generated by invasive species can minimize the damage that these species can cause to biodiversity and ecosystem services.
Tipo: Tese2022-01-01T00:00:00ZFatores controladores das concentrações de mercúrio (Hg) em organismos aquáticos costeiros da região semiárida brasileiraMoura, Victor Lacerdahttp://repositorio.ufc.br/handle/riufc/743082023-09-13T11:40:51Z2023-01-01T00:00:00ZTítulo: Fatores controladores das concentrações de mercúrio (Hg) em organismos aquáticos costeiros da região semiárida brasileira
Autor(es): Moura, Victor Lacerda
Abstract: Mercury (Hg) is naturally present in trace and ultra-trace concentrations, primarily emitted by volcanic and geothermal sources. However, human activities are contributing to increase the levels of this contaminant in ecosystems. Mercury's propensity for bioaccumulation and long tissue residence time leads to an accumulation of Hg in organisms. Other factors, such as biological and ecological considerations, could also increase Hg concentrations. In addition, environmental factors may also affect contaminant concentrations in biota. Despite several studies that have stressed the significance of these factors, little attention has been paid to the semiarid regions compared to other climatic zones. The objective of this study
was to explore the impact of environmental, biological, and ecological characteristics on the variation of Hg concentrations in organisms inhabiting an estuary in the semiarid coastal region of Brazil. Samples were collected from water, sediment, and biota from the Jaguaribe river estuary, as well as from benthic organisms in the Icaraí beach coastal zone. The sampling in Jaguaribe river was conducted at seven points within the estuarine area during
both rainy and dry periods, except for the aquatic fauna. At Icaraí beach, we collected five species of batoid fish. We measured hydrochemical parameters and quantified Hg in samples from the Jaguaribe River, and we measured the concentrations of dissolved and particulate Hg in the water samples. On Icaraí beach, we conducted total Hg, MeHg, and stable isotope quantification analyses to comprehend the significance of biological, ecological, and
environmental factors in the accumulation of Hg in these organisms in each study area. The results from both study areas reveal the significant impact of biological and ecological factors on the levels of Hg found in the biota, particularly in batoid species. In terms of environmental aspects, a notable Hg concentration variation was observed along the saline gradient in the Jaguaribe river estuary. Regions with greater marine influence demonstrated
elevated Hg concentrations and a faster accumulation rate of the contaminant in the biota. Spatially, both sediment and water samples presented comparable outcomes indicating higher levels located further from the estuary. During various climatic seasons, water, sediment, and aquatic plant samples were compared, demonstrating that the levels of Hg in the dissolved fraction, consisting of chemical compounds with significant bioavailability,
were higher in the water samples during the dry season. This finding was supported by observation of higher concentrations of Hg in floating and submerged macrophytes during the same period compared to the rainy season. The concentrations of Hg in both water and sediment suggest the possibility of Hg remobilization from sediment into the water column.
Such remobilization is more likely to occur in environments with greater marine influence, particularly during the dry season. As a result, contaminant concentrations in its dissolved form are higher in areas under greater marine influence than in those under less influence, which explains the higher levels of Hg in biota near the mouth of the affected water bodies.
Tipo: Tese2023-01-01T00:00:00ZMarginal reefs in the equatorial southwestern atlantic: benthic community heterogeneity, macroalgal blooms, and zooplankton biomassCosta, Rhayany Juvênciohttp://repositorio.ufc.br/handle/riufc/742242023-09-13T11:34:20Z2022-01-01T00:00:00ZTítulo: Marginal reefs in the equatorial southwestern atlantic: benthic community heterogeneity, macroalgal blooms, and zooplankton biomass
Autor(es): Costa, Rhayany Juvêncio
Abstract: Marginal reefs are those that occur in environments under restricted conditions, i.e., where corals occur close to environmental limits of survival or under conditions considered suboptimal, extreme or fluctuating. Thus, marginal reefs are generally associated with moderate turbidity, mesotrophic or eutrophic conditions, wide temperature variations, and/or resuspension of sediments, and are occupied by bioconstructing organisms adapted to such conditions. On these reefs there is generally a lower diversity of scleractinian corals that have adapted over evolutionary history. The resilience to environmental disturbance of coral species on marginal reefs reinforces the possible potential of these marine ecosystems as a refuge for part of the reef biodiversity in the face of ongoing climate change. However, despite growing global interest in how tropical reefs will be affected, little is known about the structure and dynamics of marginal reefs as compared to "classic" coral reefs, including aspects of the heterogeneity of benthic and planktonic communities, whose importance to reef ecology is recognized. In this context, Brazilian reefs are the only tropical reef environments in the Southwest Atlantic that are in an area considered marginal, and can be used as an important model to advance research. The objective of this research was to deepen the knowledge of the ecology of marginal reefs in the South Equatorial Atlantic from the study in three chapters in article format: (1) the spatial variation of the structure of benthic reef communities, (2) Rhizoclonium-like algal blooms, and (3) the variation in zooplankton biomass related to reef environments. Regarding benthic community structure (chapter 1), our results point to a strong spatial heterogeneity with reefs dominated by macroalgae (1 - 60%), filamentous algae (0 - 47%) and variable coverage of scleractinian corals (0 - 18%). On these reefs only four stress-tolerant massive corals occurred, with Siderastrea stellataand Montastraea cavernosa being the most abundant. The depth and the effect of swell-type waves that induce siltation of the shallower marginal reefs (16.6 - 16.7) represent important factors in the distribution of the benthic community such as sponges, algae, and corals. Another observed result refers to the occurrence of seasonal Rhizoclonium-like blooms in these marginal environments detailed in chapter 2 of the thesis. The macroalgae bloom was recorded, only between the months of May and August (2010 - 2018), forming dense mats near the reef substrate, in which they covered other organisms such as scleractinian corals, octocorals, sponges and other algae. Multivariate analysis indicates that blooms on these moderately turbid reefs are linked to increased atmospheric pressure, predominant north wind direction, and increased temperature range. Finally, in chapter 3, it was observed that in marginal reefs of turbid and low latitude zones the zooplankton biomass shows a heterogeneous distribution between different nets (65, 200 and 300 µm), with the oligotrophic characteristic of the waters and the presence of the reef formations seeming to play an important role in the distribution of the organic biomass. In this context, understanding the structure and occurrence of these benthic and planktonic communities and how they occur on marginal reefs represents a strategy of paramount importance to predict possible future scenarios, contributing to the management of these tropical reef ecosystems across the planet.
Tipo: Tese2022-01-01T00:00:00ZInfluências ambientais sobre o ecossistema halodule wrightii na costa semiárida do BrasilBarros, Kcrishna Vilanova de Souzahttp://repositorio.ufc.br/handle/riufc/736972023-07-25T12:44:07Z2013-01-01T00:00:00ZTítulo: Influências ambientais sobre o ecossistema halodule wrightii na costa semiárida do Brasil
Autor(es): Barros, Kcrishna Vilanova de Souza
Abstract: Because of anthropogenic and climate change-related pressures, there is an
increasing need of understanding on species-environment relationships. The objective of this
study was to observe environmental influences on the variations of Halodule wrightii
Ascherson in the semiarid coast of Brazil and the influences of these variations on florofaunal
associations. In 2010, four meadows of H. wrightii were mapped and the influences of rocky
and sandy bottoms and of the seasonality on shoot density, biometry and biomass were
studied. It were also observed the influences of H. wrightii changes on macroalgal and
macrofaunal communities, and also the main environmental influences, among
metheorological, physicochemical and sedimentary variables, on the seagrass variations. The
meadows were distributed in patches, parallel to the coastline, and more extensive on the
sandy bottoms. The total area sampled was of 24430 m2
, being 5800 m2
composed of dense
patches, 9100 m2
of sparse patches, 14000 m2
of nonvegetated areas, and 8000 m2
of rocks
and other reef associations (algae, zoanthids, sponges and corals). The rocky habitats had
meadows with greater shoot densities (DRY, t= -7,528; df = 43; p = 0,000; RAINY, t= -
11,038; df = 43; p = 0,000), biometry (DRY, t= -2,674; df = 47; p = 0,010; RAINY, t = -
0,172; df = 42; p = 0,863), and total biomass (DRY, t= -5,566; df = 58; p = 0,000; RAINY, t=
-6,347; df = 58; p = 0,000). Eighteen species of macroalgae were identified, classified as
epilithic (50%), epiphytes on H. wrightii (38.4%), epipsammics (8%), and epiphytes on other
algae (4%). The descriptors of this community were directly correlated to the H. wrightii
shoot density, increasing during the dry season, being more influenced by the habitat than
seasonality (PerMANOVA, F= 29,4; R2
= 0,20; p < 0,001). The macrofauna was composed
by 1108 specimens belonging to 112 taxa, highlighted crustaceans, mollusks and polichaetes.
The faunistic diversity increased during the dry season probably due to an input of infauna
because of the increase in hydrodynamic, but the abundance of epifauna seemed directly
related to the seagrass variations. Considering the seagrass habitats, the faunal descriptors
were significantly higher in the meadows of rocky bottoms, and correlated to H. wrightii
biometry and biomass. Although the fauna have been similar in vegetated and nonvegetated
areas, larvae and phytal specimens occurred only in vegetated areas. Despite the
heterogeneous environmental scenarios, the four studied sites had a similar seasonal variation,
also promoting similar seasonal alterations in the meadows. In all sites, the shoot density was
higher in the dry season (t= 0,302; df = 88; p = 0,710), whereas biometry (t= 2,909; df = 62; p
= 0,000) and biomass (t= -1,566; gl = 91; p = 0,119) were higher during the rainy season. The
variable that best explained the variations of these meadows was the time of emersion (r =
0,813). The habitat and the seasonality had a significant influence on the biology and
macrobiota associated with H. wrightii. The seasonal variations found suggested a strong
relationship with the winds and rainfall regional patterns, which should also be monitored
with the meadows, especially facing the expected climate alterations in semiarid region.
Tipo: Tese2013-01-01T00:00:00Z