João Carlos Marques - Academia.edu (original) (raw)

Papers by João Carlos Marques

InTech eBooks, Jun 21, 2017

Acta Oecologica-international Journal of Ecology, May 1, 2003

Marine Drugs

In recent years, an increased interest in marine macroalgae bioactive compounds has been recorded... more In recent years, an increased interest in marine macroalgae bioactive compounds has been recorded due to their benefits to human health and welfare. Several of their bioactivities have been demonstrated, such as anti-inflammatory, antioxidant, anticarcinogenic, antibacterial and antiviral behavior. However, there still lacks a clear definition regarding how these compounds exert their bioactive properties. Of all the bioactive compounds derived from marine macroalgae, attention has been focused on phenolic compounds, specifically in phlorotannins, due to their potential for biomedical applications. Phlorotannins are a diverse and wide group of phenolic compounds, with several structural variations based on the monomer phloroglucinol. Among the diverse phlorotannin structures, the eckol-family of phlorotannins demonstrates remarkable bioactivity, notably their anti-tumoral properties. However, the molecular mechanisms by which this activity is achieved remain elusive and sparse. This...

description of a complex system is not easy. The uncertainty and indeterminacy present in complex... more description of a complex system is not easy. The uncertainty and indeterminacy present in complex systems, drive modelers to make subjective decision about the behavior of the system and its most relevant features. This implies embedding a series of nested, and sometimes iterative and evolving assumptions in the model. This in turn, incorporates uncertainty into the model at various levels; affecting the model, the way in which it is developed and the value of its inference. But what does it mean for modelers and the way we do modeling? First, complexity affects the way in which models are implemented. Traditionally, models are thought to be developed as a sequential of three main activities: conceptualization, implementation and evaluation. However, modeling complex systems requires an iterative process of model formulation, more like a trial and error approach, where modules at different levels of detail are considered in conjunction with different assumptions and hypotheses about...

Marine and estuarine water pollution usually results from discharges of combined chemicals near t... more Marine and estuarine water pollution usually results from discharges of combined chemicals near the areas with high anthropogenic activity. Understanding mixture effects is of great importance as it may enhance the biodiversity losses. Moreover, there still exist an important knowledge gap on the toxicity resulting from multi-stress scenarios, and therefore potential synergistic effects that may arise are ignored. Thus, this study address single and equitoxic mixture effects of two formulated compounds the herbicide Primextra® Gold TZ and the metal copper by assessing toxicological endpoints in species from two trophic levels: algae growth marine diatom Thalassiosira weissflogii and immobilization estuarine calanoid copepod Acartia tonsa. Single effects revealed the herbicide Primextra® Gold TZ is considerably more toxic to diatoms: EC10=0.001 (0.0008 – 0.0013), EC20=0.002 (0.0015 – 0.0022), EC50=0.005 (0.0041 – 0.0051) mg/L, than to copepods: EC10=0.684 (0.003 – 1.314), EC20=1.003 ...

Applied Sciences, 2021

Macroalgae are a biological group that has mainly been used in Asian countries; however, the inte... more Macroalgae are a biological group that has mainly been used in Asian countries; however, the interest shown by Western society is recent, its application in the industrial sector having increased in the last few decades. Seaweeds are filled with properties which are beneficial to our health. To use them as food and enhance these properties, heat has been used on them. This process alters the bioactive compounds. If we study the levels of moisture, they can vary according to the drying methods used. High values of moisture can lead to a short shelf life due to oxidation, microbial or enzyme activity, so controlling these values is highly recommended. Heat causes enzymatic activity as well as oxidation, which leads to degradation of phenolic compounds in comparison with freeze-drying, which causes fewer losses of these components. Due to the same occurrences, lipid content can also vary, modifying the bioactive compounds and their benefits. Pigments are some of the components most aff...

Ecological Indicators, 2018

Marine pollution bulletin, 2018

Microplastic ingestion has been reported for several marine species, but the level of contaminati... more Microplastic ingestion has been reported for several marine species, but the level of contamination in transitional systems and associated biota is less known. The aim of this study was to assess the occurrence of microplastic ingestion in three commercial fish species: the sea bass (Dicentrarchus labrax), the seabream (Diplodus vulgaris) and the flounder (Platichthys flesus) from the Mondego estuary (Portugal). Microplastics were extracted from the gastrointestinal tract of 120 individuals by visual inspection and digestion solution. A total of 157 particles were extracted from 38% of total fish (96% fibers), with 1.67 ± 0.27 (SD) microplastics per fish. Significantly higher amount of ingested microplastics was recorded for D. vulgaris (73%). The dominant polymers identified by μ-FTIR were polyester, polypropylene and rayon (semi-synthetic fiber). It is reported for the first time the presence of this pollutant in fish populations from the Mondego estuary raising concerns on their ...

Cahiers De Biologie Marine, 1986

Biota Neotropica, 2016

The introduction of exotic mollusk species has resulted in loss of biodiversity in semi-arid neot... more The introduction of exotic mollusk species has resulted in loss of biodiversity in semi-arid neotropical aquatic ecosystems. This study aims to relate the presence and density of Corbicula largillierti species to human disturbance, providing data for the conservation and management of aquatic ecosystems. Specimens were collected at Epitácio Pessoa reservoir in December 2011 and June 2012, presenting densities of 20.96 and 62.89 individuals per square meter, respectively. Anthropic disturbance metrics were calculated considering the presence, type and intensity of disturbance in littoral, riparian and flood zones. The occurrence of C. largillierti was mainly associated to the variables total phosphorus (261.05 ± 342.22 µg/L) and total nitrogen (440.79 ± 103.77 µg/L), near to tributaries. The occurrence of exotic mollusk species is evidence of the need for freshwater ecosystem conservation and management, particularly in reservoirs used for water supply.

Ecological Indicators, 2016

Estuarine, Coastal and Shelf Science, 2015

Ecological Indicators, 2015

Environmental Monitoring and Assessment, 2002

Marine Ecology Progress Series, 2014

Ecological Modelling, 2008

Toxics

The use of glyphosate-based herbicides (GBHs) worldwide has increased exponentially over the last... more The use of glyphosate-based herbicides (GBHs) worldwide has increased exponentially over the last two decades increasing the environmental risk to marine and coastal habitats. The present study investigated the effects of GBHs at environmentally relevant concentrations (0, 10, 50, 100, 250, and 500 μg·L−1) on the physiology and biochemistry (photosynthesis, pigment, and lipid composition, antioxidative systems and energy balance) of Ulva lactuca, a cosmopolitan marine macroalgae species. Although GBHs cause deleterious effects such as the inhibition of photosynthetic activity, particularly at 250 μg·L−1, due to the impairment of the electron transport in the chloroplasts, these changes are almost completely reverted at the highest concentration (500 μg·L−1). This could be related to the induction of tolerance mechanisms at a certain threshold or tipping point. While no changes occurred in the energy balance, an increase in the pigment antheraxanthin is observed jointly with an incre...

Processes, 2021

The exponential increase of the human population demands the overuse of fertilizers and pesticide... more The exponential increase of the human population demands the overuse of fertilizers and pesticides in agriculture practices to suppress food production needs. The excessive use of these chemicals (fertilizers and pesticides) can comport deleterious effects to the ecosystems, including aquatic systems and communities. Oxyfluorfen is a fluorine-based herbicide, and its application has increased, since it is seen as an alternative to control glyphosate-resistant weeds. Copper sulfate is an inorganic pesticide based on copper which is being used in several chemical formulations, and it is the second main constituent of fungicides. Besides the known effects of such products in organisms, climatic changes pose an additional issue, being a main concern among scientists and politicians worldwide, since these alterations may worsen ecosystems’ and organisms’ sensitivity to stress conditions, such as the exposure to pollutants. Thalassiosira weissflogii (Grunow) G. A. Fryxell & Hasle, 1977 pl...