43 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)
Ergogenic effects of caffeine on performance
The caffeine is a substance that doesn't present nutricional value being classified as an alkaloid with pharmacological effects of stimulating action on central nervous system (CNS). However, this substance has been considered a nutritional aid by being present in several drinks consumed daily, such as coffee, coke, teas, and some soft drinks with guarana in its composition. The use of this substance has became quite common in the sports through the years, particularly for athletes that dispute resistance competition. The possibility of improvement of the physical performance put this alkaloid in the list of prohibited substances for the International Olympic Committee (COI), which established the limit of 12 caffeine pg/ml in the urine as parameter for doping detection. Some studies have been demonstrating that those levels can be reached with the ingestion of approximately 9 mg/kg of body weight of caffeine. Though, more recent studies have been evidencing improvement in the athletic performance with ingestion of just 3 to 6 mg/kg for body weight of caffeine. Such observations seem to place in risk the tolerable limit specified by COI, what could favor the improvement of the performance by the users. These facts demonstrate the need of more investigations on the ergogenic effect of the amount of caffeine ingestion and possibly of revision on the tolerable levels to be ingestedA cafeína é uma substância que não apresenta valor nutricional, sendo classificada como um alcalóide farmacologicamente ativo, estimulante do sistema nervoso central (SNC). No entanto, esta substância tem sido considerada um ergogênico nutricional por estar presente em várias bebidas consumidas diariamente, tais como o café, o chocolate, o mate, e algumas bebidas suaves à base de guaraná. O seu uso tem-se tornado bastante comum no meio esportivo, principalmente nos últimos anos, particularmente por atletas que disputam provas de resistência. A possibilidade de melhora do desempenho físico fez com que este alcalóide entrasse na lista de substâncias proibidas pelo Comitê Olímpico Internacional (COI), o qual estabeleceu o limite de 12 jig/ml de cafeína na urina como parâmetro para detecção de “doping” Alguns estudos têm demonstrado que esses níveis podem ser alcançados com a ingestão de aproximadamente 9 mg de cafeína por quilograma de peso corporal. Todavia, estudos mais recentes têm evidenciado melhora no desempenho atlético com a ingestão de apenas 3 a 6 mg de cafeína por quilograma de peso corporal. Tais observações parecem colocar em risco o limite tolerável estipulado pelo COI, o que poderia favorecer a melhoria do rendimento por parte dos usuários. Esses fatos demonstram a necessidade de maiores investigações sobre o efeito ergogênico de diferentes dosagens de cafeína e, possivelmente, de revisão dos níveis de ingestão tolerávei
Zooplankton distribution in a marine protected area: the Berlengas Natural Reserve (Western Coast of Portugal)
Zooplankton distribution in the Berlengas Natural Reserve (Portugal) was studied over a period of one year (February 2006 to February 2007). Monthly sampling was performed at 6 stations, differentiated according to depth and distance to the coastline. The aim of this study was to investigate the overall zooplankton variability through its different dimensions (space vs. time). The Partial Triadic Analysis (PTA) was used to study the spatial variability of the zooplankton community and its dynamics in time and the dynamic trajectories of the zooplankton species for each site. It was possible to distinguish a neritic-ocean gradient of the zooplankton composition and a temporal variability. Four distinct periods can be highlighted considering the distribution of the dates and the arrangement of the species: (i) the first one comprised August to November, (ii) the second one was related to June and July, (iii) the third one associated with spring (April and May) and, (iv) the latest one was related to winter (February, March and December 2006 and January and February 2007). The PTA method showed the similarities between the successive data tables and proved to be useful for investigating biotic structures and detecting spatial-temporal patterns in zooplankton distribution.publishe
Zooplankton distribution in a marine protected area: The Berlengas Natural Reserve, Western Coast of Portugal
Zooplankton distribution in the Berlengas Natural Reserve (Portugal) was studied over a period of one year
(February 2006 to February 2007). Monthly sampling was performed at 6 stations, differentiated according to depth and distance to the coastline. The aim of this study was to investigate the overall zooplankton variability through its different dimensions (space vs. time). The Partial Triadic Analysis (PTA) was used to study the spatial variability of the zooplankton community and its dynamics in time and the dynamic trajectories of the zooplankton species for each site. It was possible to distinguish a neritic-ocean gradient of the zooplankton composition and a temporal variability. Four distinct periods can be highlighted considering the distribution of the dates and the arrangement of the species: (i) the first one comprised August to November, (ii) the second one was related to June and July, (iii) the third one associated with spring (April and May) and, (iv) the latest one was related to winter (February, March and December 2006 and January and February 2007). The PTA method showed the similarities between the successive data tables and proved to be useful for investigating
biotic structures and detecting spatial-temporal patterns in zooplankton distribution.info:eu-repo/semantics/publishedVersio
MarinEye - A tool for marine monitoring
This work presents an autonomous system for marine integrated physical-chemical and biological monitoring – the MarinEye system. It comprises a set of sensors providing diverse and relevant information for oceanic environment characterization and marine biology studies. It is constituted by a physicalchemical water properties sensor suite, a water filtration and sampling system for DNA collection, a plankton imaging
system and biomass assessment acoustic system. The MarinEye system has onboard computational and
logging capabilities allowing it either for autonomous operation or for integration in other marine observing systems (such as Observatories or robotic vehicles. It was designed in order to collect integrated multi-trophic monitoring data. The validation in operational environment on 3 marine observatories: RAIA, BerlengasWatch and Cascais on the coast of Portugal is also discussed.info: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 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
Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences
The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & Nemésio 2007; Donegan 2008, 2009; Nemésio 2009a–b; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported
by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on
18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based
researchers who signed it in the short time span from 20 September to 6 October 2016
Eleições municipais comparadas: a escolha do chefe do executivo no Brasil e no Uruguai e o impacto sobre os sistemas partidários locais (2000-2005)
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