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Conference: “Effects of seaweeds, nutrients and sedimentation on seagrass and seagrass-associated fauna”

Annual Biology Conference (ABC) 2016, University of Canterbury, New Zealand

08-abc-conference-2016

Alfonso Siciliano, Mads S. Thomsen, David R. Schiel

X

Abstract

Seagrasses are marine plants that take up nutrients, stabilize sediments, increase habitat complexity and thereby also increase biodiversity of sedimentary coastal ecosystems. Seagrasses also facilitate seaweeds that can become entangled around seagrass leaves and stems. However, relatively little is known about interactions between entangled seaweeds and seagrass, their effects on seagrass-associated invertebrates and if their interactions are modified by abiotic conditions, like nutrient and sedimentation levels. We aimed to test the hypotheses that (i) seaweeds have negative effects on seagrass (competing for limited resources) but positive effect on invertebrate biodiversity (by increasing habitat-complexity), across seasons in the Avon-Heathcote estuary, (ii) that similar processes occur in other estuaries, and (iii) that the magnitude of effects increases with increasing levels of inorganic nutrients and sediments. To test the first two hypotheses, we collected cores from the Avon-Heathcote estuary and from six other estuaries. To test the third hypothesis, we manipulated nutrient and sedimentation levels in two field-experiments. Preliminary data analysis supports our hypotheses: seaweeds had negative impact on seagrass but positive effects on the abundance of many invertebrates. We also found that enhanced sediments, but not nutrients, had strong negative impact on seagrass with cascading negative impacts on the invertebrate community.

3D modelling

Having fun while doing research… or doing research while having fun?!?!?

The new frontiers of technology are starting paying dividends for me as well, finally. I’m talking about 3D modelling. A couple of months ago I finalize my morphological analysis on Cystophora species (I’ll be talking about them in another article) mainly aimed to test the hypothesis that a different morphology can be a good driver for clients (abundance, biodiversity, ecc). Scientific literature has already reported how biogenic architecture can be extremely relevant for invertebrates in intertidal and subtidal marine communities and many ways have been found to study, quantifying and comparing the tridimensionality of key-stone or common species.

 

My research in this field started with high-quality pictures and since I’m very keen in graphics… well, I ended up with looking for informations about 3d modelling.

During my studies in experimental ecology, I’ve used (and I’m currently using) lot of different materials with different shape and size in order to emulate habitat-formers and epiphytes, for morphological reasons and ecological processes.
Here is when 3D modelling can help research in testing how several variables are affected by some specific factors.

That’s a good chance to mention a free software (with additional feature through payment): Autodesk Memento, with the new version Autodesk Remake, is an excellent software able to manage with a series of pictures or scans from laser or 3D scanners and output a tridimensional model.

Obviously I’ve already tried it (how to resist?!?!) with a Canon Powershot G15, collecting a series of sequential 360 degrees pictures at different height with the right light and background. Creating a 3D model can be really easier than the expected if you do it in the right way.

Here are a couple of models I’ve created some months ago. The mussel was kind of 15 cm while the cockle was more and less 2-2.5 cm long.
They are definitely incredibly accurate (note all the epibionts living in the mussel) and the resolution is excellent (thanks the camera) allowing in some case really complex analysis.
Their use is mainly addressed to test the role of this organisms in their habitat, defining the consequences of replacing them with mimics or modifying some factors strictly related with their ecology or morphology (temperature, color, rugosity, etc).

 

 

 

What next? Well, I’ll post something… :)

Conference: “Epiphytism as key driver of biodiversity in canopy-forming seaweeds-dominated systems”

11th International Temperate Reefs Symposium (ITRS) 2016, University of Pisa, Italy

06-itrs-2016

Alfonso Siciliano, Mads S. Thomsen, David R. Schiel

X

Abstract

It is well established that host species that are morphologically and genetically different can support different epibiotic species, and that these differences can support different invertebrate communities. However, no studies have tested the opposite hypothesis of whether morphologically similar congeneric hosts support similar epibiota and have similar cascading effects on invertebrate communities. This hypothesis was tested with mensurative and manipulative experiments using three conspecific, morphologically similar marine seaweed hosts: the canopy-forming fucoids Cystophora torulosa, C. scalaris, and C. retroflexa. In the mensurative experiment, hosts, epiphytes and associated invertebrate communities were sampled and enumerated from 4 tide-pools (>1 m apart), at 2 reefs (>1 km apart) and 4 sites (>100 km apart). In two follow-up manipulative experiments, defaunated hosts, epiphytes and epiphytes’ mimics were combined and transplanted to shared tide pools and the epifaunal recolonization was quantified. Both experiments suggest that epiphytism increases abundances and richness of invertebrates, across host species, epiphyte species, sites, regions, and experimental methods, demonstrating its key role in sustaining the epifaunal community. However, the experiments reject the initial hypothesis since congeneric and morphologically similar hosts appear to support a different epifauna and having different cascading effects.

Biomarkers and bioindicators

According to Depledge (1993), a biomarker can be defined as:

… a biochemical, cellular, physiological or behavioural variation that can be measured in tissue or body fluid samples at the level of the whole organism (either individuals or populations) that provides evidence of exposure to and/or effects of one or more chemical pollutants (and/or radiations).

Then, using biomakers can allow us to predict the occurrence of negative effects through the analysis of immediate responses. And that is why the use of biomarkers is very widespread in environmental bio-ecology and biomonitoring:
– they offer an integrate response of the bioindicator exposure, considering absorption and exposure ways;
– they offer an integrate response of the toxicological interactions and pharmacokinetic properties of the mixture of pollutants around the bioindicator;
– they provide an immediate response to exposure to toxic agents that can be used to predict long-term effects.

Bioindicators can be considered all the organisms (a parts of them) that can provide informations about environmental quality (or part of it) through specific reactions, for example biochemical, physiological, morphological, etc.

For that it is important that they meet some requirements:
– ecological optimum and wide distribution in the study area;
– easy identification and enough knowledge of the species (physiologically, anatomically, ecologically);
– genetic uniformity and long life cycle;
– low mobility and easy availability in all seasons.

Nuclear abnormalities and micronucleous are the final expression of genotoxic agents damage. They are formed during an incorrect mitotic anaphase, when isolated nuclear elements (chromosomal fragments or acentric chromosomes) form one or more smaller secondary cores in the new forming cell(s).

Materials and methods

In my case of study, I used:

– a benthic fish, Parablennius sanguinolentus, as bioindicator

– nuclear abnormalities and micronucleous in eritrocytes as biomarker

in order to verify and quantify the damage caused by the presence of anthropogenical chemical pollutants (PAHs, benzo(a)pyrene, benzo(k)fluoranthene, heavy metals) in two sites of the Eastern Coast of Sicily (Italy).

The data were then combined with chemical analysis of water and sediments, bioaccumulation values of heavy metals in the muscles and skeletal abnormalities for an integrate environmental perspective.

For each sample, the methods included:

– data acquisition;

– blood sample with blood smear;

– muscles sample for heavy metals analysis;

– sample preservation for skeletal abnormalities analysis.

During the analysis on microscope the erythrochytes were divided in:

– normal (NE);

– abnormal (AE);

– micronucleous (MN).

Their relative frequence (FMN‰, FAN‰) was used in order to estimate the genotoxic damage.

Results

Several studies have shown that erythrochytes of peripheral blood of fish have a high micronucleous percentage as results of different pollutants exposure.

In my case of study, I compared two sites with different pollutants level, one used as virtual reference and the other as high polluted area. In the latter, the incidence of anthropogenical contaminants was statistically significant, supporting others authors’ data on skeletal abnormalities (due to Cd), bioaccumulation of heavy metals in muscles (Zn and Pb) and chemical contaminants in water and sediments.

Chemical contaminants had an incidence on nuclear abnormalities (measured in FAN ‰M) of 326.4 against 69.4 in the reference site, 4.7 times higher, while the incidence on micronucleous formation (measured in FMN ‰M): was 11.8 against 0.5, more than 23 times higher.

MICRONUCLEOUS COMPARISON
LOW INCIDENCE


HIGH INCIDENCE


Conference: “Cascading effects of epiphytism associated with co-occurring congeneric hosts”

New Zealand Ecological Society conference (NZES) 2015, University of Canterbury, New Zealand

03-nzes-conference-2015

Alfonso Siciliano, Mads S. Thomsen, David R. Schiel

X

Abstract

It is well established that host species that are morphologically and genetically different can support different epibiotic species, and that these differences can support different invertebrate communities. However, no studies have tested the opposite hypothesis of whether morphologically similar congeneric hosts support similar epibiota and have similar cascading effects on invertebrate communities. This hypothesis was tested with mensurative and manipulative experiments using three conspecific, morphologically similar marine seaweed hosts: the canopy-forming fucoids Cystophora torulosa, C. scalaris, and C. retroflexa. In the mensurative experiment, hosts, epiphytes and associated invertebrate communities were sampled and enumerated from 4 tide-pools (>1 m apart), at 2 reefs (>1 km apart) and 4 sites (>100 km apart). In two follow-up manipulative experiments, defaunated hosts, epiphytes and epiphytes’ mimics were combined and transplanted to shared tide pools and the epifaunal recolonization was quantified. Both experiments suggest that epiphytism increases abundances and richness of invertebrates, across host species, epiphyte species, sites, regions, and experimental methods, demonstrating its key role in sustaining the epifaunal community. However, the experiments reject the initial hypothesis since congeneric and morphologically similar hosts appear to support a different epifauna and having different cascading effects.