13 research outputs found
Environmental forcing of an estuarine gradient of zooplankton abundance and production
Doutoramento em BiologiaOs copépodes são pequenos e frágeis crustáceos que constituem um
dos grupos de organismos metazoários mais abundantes do mundo.
Em ambientes marinhos e estuarinos, os copépodes assumem um
papel de extrema relevância ao nível das cadeias tróficas,
nomeadamente na transferência de matéria e energia de níveis tróficos
inferiores (fitoplâncton) para níveis tróficos superiores (ex. larvas de
peixe). A importância ecológica dos copépodes reflecte-se no elevado
número de citações constantes no ISI Web of Knowledge (7716
citações entre 1969 e 2006) e no destaque que os mesmos continuam
a possuir em estudos recentes de planctologia marinha e estuarina.
Esta dissertação teve como objectivos principais (1) descrever
variações espacio-temporais em termos de abundância e biomassa de
populações estuarinas de copépodes da Ria de Aveiro (Portugal) e a
sua relação com parâmetros hidrológicos (salinidade, temperatura,
clorofila a e precipitação; (2) comparar as taxas de crescimento e
desenvolvimento de populações alopátricas de copépodes; (3) definir
modelos de crescimento dependentes da temperatura para as formas
juvenis (nauplius e copepoditos) de Acartia tonsa; (4) avaliar o
forçamento ambiental na distribuição e abundância de populações de
Acartia e (5) calcular taxas de produção secundária potenciais para as
populações de Acartia. Numa primeira fase, foi objecto de estudo a
comunidade de copépodes estuarinos, para a qual foram descritos os
padrões temporais de abundância e biomassa e obtidas estimativas de
produção secundária. Os resultados obtidos neste estudo permitiram
concluir que, entre outros aspectos, a abundância e biomassa da
comunidade de copépodes da Ria de Aveiro se encontra
significativamente correlacionada de modo positivo com a salinidade e
com a temperatura da água. As estimativas das taxas de produção
secundária derivadas da aplicação de modelos gerais de crescimento
mostraram ser algo diferentes, sendo a estimativa dada pelo modelo de
Hunthey & Lopez (1992) mais elevada do que a obtida pelo modelo de
Hirst & Bunker (2003). O crescimento e desenvolvimento de espécies
de Acartia foram estudados sob condições controladas em termos de
alimento e temperatura, de forma a serem definidos modelos de
crescimento dependentes da temperatura. A partir destes estudos
concluiu-se que as populações alopátricas possuem diferentes
respostas à temperatura. Além deste aspecto, também se observou
que, pelo menos no caso da A.tonsa, as taxas de crescimento das
formas juvenis (nauplius e copepoditos) estimadas in situ ou sob
condições saturantes de alimento são similares.
resumo
O forçamento ambiental das populações de Acartia no Canal de Mira foi
avaliado através de uma análise de componentes principais (ACP), que
permitiu a análise simultânea das alterações espaciais e temporais das
diferentes populações. Esta análise identificou três zonas distintas no
estuário com base na abundância de Acartia spp.. Para cada zona,
análises de correlação com diferentes desfasamentos temporais entre
as variáveis ambientais e a abundância de copépodes, permitiram
detectar a existência de forçamentos ambientais específicos, assim
como um efeito positivo da biomassa fitoplanctónica na abundância do
zooplâncton verificada meses mais tarde. Esta tese demonstrou
igualmente a grande importância que as populações de Acartia,
especialmente a mais abundante – A. tonsa – assumem na
transferência de matéria e energia no ambiente planctónico da Ria de
Aveiro (Portugal).Copepods are small fragile and tiny crustaceans that form one of the
world’s most abundant groups of metazoan organisms. In estuarine and
marine environments copepods assume a key role in what trophic
chains are concerned, namely in the transfer of matter and energy from
lower trophic levels (phytoplankton) to higher trophic levels (ex. fish
larvae). Copepods ecological importance is proven by the high number
of quotations in ISI Web of Knowledge (7716 quotations between 1969
and 2006) and in the significance that they still have concerning current
studies on estuarine and marine planktonic studies. The main goals of
the present thesis were (1) to characterize and to describe the spatialtemporal
patterns of abundance, biomass and production of the
estuarine copepod community from Ria de Aveiro (Portugal) and its
relationship with hydrological data (salinity, temperature, chlorophyll a
and rainfall regime); (2) to compare growth and developmental rates of
allopatric copepod populations; (3) to define temperature dependent
growth models for nauplii and copepodites of Acartia tonsa; (4) to
evaluate environmental forcing on the distribution and abundance of
Acartia populations; and (5) to estimate potential secondary production
rates of Acartia populations. In a first stage estuarine copepods
community was studied, time patterns of abundance and biomass
having been described and estimates of secondary production having
been obtained. Results achieved by this study have led us to the
conclusion that, among other aspects, abundance and biomass of the
copepods community in Ria de Aveiro is positively correlated with water
salinity and temperature. Estimates of secondary production rates
deriving from the use of general growth models were different, the
estimate obtained by Hunthey & Lopez (1992) model being higher than
the one resulting from the Hirst & Bunker (2003) one. In order to define
specific temperature-dependent copepod growth models, the growth
and development of Acartia species were studied under controlled
conditions of food and temperature. From those studies it was
concluded that allopatric populations have different temperature
responses. Additionally, it was also observed that, at least for A.tonsa,
the growth rates of nauplii and copepodites at saturated food conditions
and in situ conditions of food are similar.
Environmental forcing of Acartia populations in Canal de Mira was
evaluated by means of 3-mode PCA, which analyses simultaneously
spatial and temporal changes of multispecies assemblages. This
analysis identified three distinct zones along the estuary based on
Acartia spp. abundance. For each zone time-lagged correlations
between environmental variables and copepods abundance indicated
that different zones were forced by different combinations of variables
and the existence of delayed effects of phytoplanktonic biomass on the
abundance of A.tonsa. This thesis also demonstrated the high
importance that Acartia populations, in particular the most abundant
A.tonsa, assume on the transfer of matter and energy in the planktonic
realm of Ria de Aveiro (Portugal)
Pervasive gaps in Amazonian ecological research
Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4
While the increasing availability of global databases on ecological communities has advanced our knowledge
of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In
the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of
Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus
crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced
environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian
Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by
2050. This means that unless we take immediate action, we will not be able to establish their current status,
much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio
Pervasive gaps in Amazonian ecological research
Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost
Pervasive gaps in Amazonian ecological research
Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost
Catálogo Taxonômico da Fauna do Brasil: setting the baseline knowledge on the animal diversity in Brazil
The limited temporal completeness and taxonomic accuracy of species lists, made available in a traditional manner in scientific publications, has always represented a problem. These lists are invariably limited to a few taxonomic groups and do not represent up-to-date knowledge of all species and classifications. In this context, the Brazilian megadiverse fauna is no exception, and the Catálogo Taxonômico da Fauna do Brasil (CTFB) (http://fauna.jbrj.gov.br/), made public in 2015, represents a database on biodiversity anchored on a list of valid and expertly recognized scientific names of animals in Brazil. The CTFB is updated in near real time by a team of more than 800 specialists. By January 1, 2024, the CTFB compiled 133,691 nominal species, with 125,138 that were considered valid. Most of the valid species were arthropods (82.3%, with more than 102,000 species) and chordates (7.69%, with over 11,000 species). These taxa were followed by a cluster composed of Mollusca (3,567 species), Platyhelminthes (2,292 species), Annelida (1,833 species), and Nematoda (1,447 species). All remaining groups had less than 1,000 species reported in Brazil, with Cnidaria (831 species), Porifera (628 species), Rotifera (606 species), and Bryozoa (520 species) representing those with more than 500 species. Analysis of the CTFB database can facilitate and direct efforts towards the discovery of new species in Brazil, but it is also fundamental in providing the best available list of valid nominal species to users, including those in science, health, conservation efforts, and any initiative involving animals. The importance of the CTFB is evidenced by the elevated number of citations in the scientific literature in diverse areas of biology, law, anthropology, education, forensic science, and veterinary science, among others
Culturas laboratoriais de Diatomáceas marinhas: perfis de Exopolissacarídeos
Foi objectivo principal deste trabalho a identificação
de espécies diatomológicas marinhas produtoras de
exopolissacarídeos e a sua caracterização. Para tal, e
partindo de amostras de plâncton e de bentos recolhidas no
Canal de Navegação da Ria de Aveiro, foram obtidas, após
amplificação e isolamento, 19 culturas unialgais.
De entre elas, foram escolhidas 6 que sofreram um
processo de axenização. Em resultado deste processo,
somente se obtiveram culturas axénicas de Navicula directa
(W. Smith) Ralfs, Amphora holsatica Hustedt e Melosira
nummuloides (Dillwyn) Agardh.
Para estes 3 taxa quando cultivados em meio de
cultura limitado, foi determinada a respectiva curva de
crescimento, e relacionada com a consequente variação da concentração dos nutrientes no meio (NO3-, PO43- e SiO2) ao
longo do tempo de cultivo.
Para além do modo de crescimento, foram também
determinados os padrões de produção de hidratos de
carbono celulares e extracelulares elaborados pelos taxa, ao
longo do tempo de incubação. Os padrões de produção de
hidratos de carbono extracelulares foram posteriormente
relacionados com a respectiva curva de crescimento e com
a variação da concentração de nutrientes presentes no meio
de cultura.
Por último, procedeu-se à determinação da
composição dos hidratos de carbono extracelulares em
termos de açucares simples e conteúdo em ácidos urónicos.
Concluiu-se que, os taxa em causa elaboram e
exudam quantidades diferentes de hidratos de carbono, que
tal exudação ocorre quando a concentração dos nutrientes
presentes no meio diminui, e que a máxima produção foi
atingida durante a fase estacionária.
Através do isolamento e caracterização dos
polímeros presentes no meio de cultura de Navicula directa
(W. Smith) Ralfs, Amphora holsatica Hustedt e Melosira
nummuloides (Dillwyn) Agardh, conclui-se que se tratavam
de polissacarídeos (exopolissacarídeos). Estes mostraram
ser bastante semelhantes entre si, sendo no geral
considerados como um polímero de ácidos urónicos.
Poderão existir no entanto certas diferenças em termos de
composição em açúcares simples, facto em parte
comprovado durante este estudo.The aim of this work was to identify marine diatom
species that produce and exudate exopolysaccharides, and
also to characterise such polymers. Therefore, plankton and
benthos samples were collected in the Canal de Navegação
– Ria de Aveiro, and after the amplification and isolation, 19
monospecific algal cultures were obtained.
Six of the 19 microalgal cultures maintained in
laboratorial conditions, were submitted to an axenic process
by the use of an antibiotic solution. Axenic cultures were
successfully obtained for Navicula directa (W. Smith) Ralfs,
Amphora holsatica Hustedt and Melosira nummuloides
(Dillwyn) Agardh.
The growth curve of those 3 taxa in batch cultures
were then determined and compared with the concentration of nutrients (NO3-, PO43- and SiO2) in the medium, during the
experimentation period.
The pattern of cellular and extracellular carbohydrate
production was also defined in those 3 axenic cultures of
marine diatoms. For each culture, the carbohydrate
production was compared with the growth curve and with the
variation of nutrient concentration in the medium.
The analysis of neutral sugars and uronic acids was
performed for the exopolysaccharides isolated from the
culture media of Navicula directa (W. Smith) Ralfs, Amphora
holsatica Hustedt and Melosira nummuloides (Dillwyn)
Agardh.It was concluded that the 3 marine diatoms produced
and exudated different amounts of carbohydrates, and that
the exudation process was more important when the media
were almost nutrient-depleted, and also when the species
reached the stationary growth phase.
The exopolysaccharides produced by the three
species, mainly polymers of uronic acids, are very similar.
However, the results suggest that certain differences in the
composition of neutral sugars may occur.Mestrado em Ciências das Zonas Costeira
NEOTROPICAL ALIEN MAMMALS: a data set of occurrence and abundance of alien mammals in the Neotropics
Biological invasion is one of the main threats to native biodiversity. For a species to become invasive, it must be voluntarily or involuntarily introduced by humans into a nonnative habitat. Mammals were among first taxa to be introduced worldwide for game, meat, and labor, yet the number of species introduced in the Neotropics remains unknown. In this data set, we make available occurrence and abundance data on mammal species that (1) transposed a geographical barrier and (2) were voluntarily or involuntarily introduced by humans into the Neotropics. Our data set is composed of 73,738 historical and current georeferenced records on alien mammal species of which around 96% correspond to occurrence data on 77 species belonging to eight orders and 26 families. Data cover 26 continental countries in the Neotropics, ranging from Mexico and its frontier regions (southern Florida and coastal-central Florida in the southeast United States) to Argentina, Paraguay, Chile, and Uruguay, and the 13 countries of Caribbean islands. Our data set also includes neotropical species (e.g., Callithrix sp., Myocastor coypus, Nasua nasua) considered alien in particular areas of Neotropics. The most numerous species in terms of records are from Bos sp. (n = 37,782), Sus scrofa (n = 6,730), and Canis familiaris (n = 10,084); 17 species were represented by only one record (e.g., Syncerus caffer, Cervus timorensis, Cervus unicolor, Canis latrans). Primates have the highest number of species in the data set (n = 20 species), partly because of uncertainties regarding taxonomic identification of the genera Callithrix, which includes the species Callithrix aurita, Callithrix flaviceps, Callithrix geoffroyi, Callithrix jacchus, Callithrix kuhlii, Callithrix penicillata, and their hybrids. This unique data set will be a valuable source of information on invasion risk assessments, biodiversity redistribution and conservation-related research. There are no copyright restrictions. Please cite this data paper when using the data in publications. We also request that researchers and teachers inform us on how they are using the data
NEOTROPICAL XENARTHRANS: a data set of occurrence of xenarthran species in the Neotropics
Xenarthrans—anteaters, sloths, and armadillos—have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, 10 anteaters, and 6 sloths. Our data set includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the southern United States, Mexico, and Caribbean countries at the northern portion of the Neotropics, to the austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n = 5,941), and Cyclopes sp. have the fewest (n = 240). The armadillo species with the most data is Dasypus novemcinctus (n = 11,588), and the fewest data are recorded for Calyptophractus retusus (n = 33). With regard to sloth species, Bradypus variegatus has the most records (n = 962), and Bradypus pygmaeus has the fewest (n = 12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other data sets of Neotropical Series that will become available very soon (i.e., Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans data set. Please cite this data paper when using its data in publications. We also request that researchers and teachers inform us of how they are using these data