Looking for internship in bioacoustics and marine ecology ?

 We are currently looking for an little helper to work on the influence of noise pollution on marine invertebrates.

More information on NIOZ website :

https://www.nioz.nl/en/education/internships/underwater-noise-pollution-and-marine-invertebrate-health

Please contact me if interested :)

A few words on MSFD

The EU "Marine Strategy" Framework Directive (MSFD) aims at protecting more efficiently the marine environment across Europe.

Source: http://msfd.eu/

In order to achieve a so-called "Good Ecological Status" (GES), i.e. maintaining biodiversity and ecosystem services with sustainable human influence on the marine environment, it integrates the concepts of environmental protection and sustainable use in a legislative framework requiring each Member State to develop a strategy for its marine waters.

Beside MSFD, other EU Directives aim at managing the marine environment and the ressources it provides to humans (e.g. Water Framework Directive, Common Fisheries Policy). However, MSFD is to date the only environmental Directive considering the marine environment as a whole (i.e. not limited to coastal areas), connections between ecosystem compartments (foodwebs) and with human activities acting on them (including socio-economic impact of environmental degradation).


Marine strategies of each Member State include :

 - an assessment of current environmental status of national marine waters and the environmental impact of human activities in these waters as well as a socio-economic analysis of human activities in the concerned regions,

- a definition of GES for national marine waters,

- environmental targets to achieve GES and indicators to be used in order to evaluate management measures,

- a programme of measures to achieve or maintain GES.


These marine strategies follow an adaptive management approach and must be kept up-to-date and reviewed every 6 years. The second cycle will start in 2018.

Source: http://ec.europa.eu/

The Directive sets 11 quantitative descriptors of GES for the marine environment. These descriptors are set to help Member States interpret the practical meaning of GES:

    Descriptor 1. Biodiversity is maintained

    Descriptor 2. Non-indigenous species do not adversely alter the ecosystem

    Descriptor 3. The population of commercial fish species is healthy

    Descriptor 4. Elements of food webs ensure long-term abundance and reproduction

    Descriptor 5. Eutrophication is minimised

    Descriptor 6. The sea floor integrity ensures functioning of the ecosystem

    Descriptor 7. Permanent alteration of hydrographical conditions does not adversely affect the ecosystem

    Descriptor 8. Concentrations of contaminants give no effects

    Descriptor 9. Contaminants in seafood are below safe levels

    Descriptor 10. Marine litter does not cause harm

    Descriptor 11. Introduction of energy (including underwater noise) does not adversely affect the ecosystem

In line with Regional Seas Conventions (OSPAR, Barcelona Convention, HELCOM), the assessment of GES for each descriptor relies on the use of adequate indicators computed from monitoring data collected by the Member States. Accordingly, GES assessment can necessitate the development of assessment tools/indicators and the implementation of apppropriate monitoring programmes. Different strategies can be used by the Member States to reach these goals depending on the determination of what GES means for their national waters.

Paper accepted for publication in Functional Ecology!

I recently wrote a review article that has now been accepted for publication in Functional Ecology on how eutrophication influences host-parasite interactions (link). Here is also a link to read the lay summary, available on the webpage of the journal.

Better fed host does not necessarily imply more resources for parasites

Increases in phytoplankton biomass following nutrient enrichment can impact host-parasite interactions by altering the amount of resources that parasites can acquire during an infection. As parasite fitness is primarily affected by the quality of the host as a resource (i.e. the nutritional quality of the host and, by extension, host body condition), a positive relationship between host body condition and parasite fitness was evidenced in a number of systems impacted by anthropogenic eutrophication such as parasite-induced malformations in amphibians (Johnson et al. 2007), whirling disease and proliferative kidney disease in salmonids (Hartikainen etal. 2009) and swimmer’s itch (Soldánová etal. 2013).

Male threespine stickleback in eutrophied waters during breeding season

However, it should be noted that better fed host does not necessarily imply more resources for parasites because higher food resources for hosts as a result of eutrophication can also limit parasite proliferation by promoting host resistance to infection (Aalto, Decaestecker & Pulkkinen 2015). Such a negative influence of nutrient enrichment on parasite transmission is poorly documented in the literature. An exception is the study by Anaya‐Rojas et al.(2016). Using mesocosms, the authors investigated the connections between nutrient loading, parasitism and host condition using the monogenean parasite Gyrodactylus spp. and the threespine stickleback Gasterosteus aculeatus. The parasite reproduces on the host skill and gills and transmission is directly connected to host density (Bakke, Cable & Harris 2007). By controlling fish density in mesocosms and by manipulating nitrogenous nutrient (NaNO₃ and HNa₂PO₄) loading and exposure to parasites, the authors found fish assigned the low nutrient treatment to be in worse condition, with lower stomach fullness compared to fish assigned to high nutrient treatment (Anaya‐Rojas et al. 2016). For sticklebacks originating from the lake ecotype, where Gyrodactylus spp. load is high, nutrient enrichment was negatively correlated to parasite load, but this was not true for fish originating from the stream ecotype, where prevalence is lower. Additionally, more sticklebacks from the lake ecotype died after being exposure to parasites during the experiment, indicating a higher sensitivity to Gyrodactylus infection compared to fish from the stream ecotype. This led the authors to hypothesize that lake sticklebacks might alter their diet or feeding rate in order to better cope with Gyrodactylus spp. (Anaya‐Rojas et al. 2016). 

Communication between phages alters infection spread in bacterial populations

A growing amount of research evidences how co-infections can alter infection likelihood in a wide range of organisms. Most of this work has focused on how weakened host defences can facilitate new infections, hence contributing to the spread of directly-transmitted parasites in a population. This situation can lead to vicious circles and trigger disease outbreaks (reviewed in Beldomenico & Begon 2010). The work by Erez et al. (2017) presents new perspectives on how infections can disease spread in host populations.

This work focuses on phages infecting bacteria (Bacillus subtilis). These pathogens can enter lytic or lysogenic life-cycle when invading the host. While the lytic cycle allows high replication from the phage, its strong virulence also leads to the death of the host. Phage lysogeny implies the phage to integrate the host DNA, providing it resistance against further infection from the same pathogen, and replicates with the host cellular division without killing the host. Lytic life-cycle is thought to be advantageous when hosts are abundant in the environment while lysogeny is seen as an advantage when the probability of infecting new host cells is low (see Chibani-Chennoufi et al. 2004). However, the mechanisms inducing lytic over lysogenic transmission are still poorly known (Davidson 2017). 

source for picture: http://www.nature.com/nature/journal/vaop/ncurrent/images_article/nature21118-f1.jpg

The study by Erez et al. evidences that communication between phages can influence life-cycle determination in phages. By infecting B. Subtilis bacteria with four different phages, the authors found one of the phages, phi3T, to protect hosts from infections by the same pathogen by promoting phage lysogeny. The authors suggested that the phage protein AimP triggers the release of a peptid fragment they called Arbitrium from infected cells. When this compound is taken up by neighbouring cells, high concentrations would favour lysogeny while low concentrations would favour lytic infections by phages. This study is the first to evidence such a quorum sensing mechanism in phage and could change our perception of life-cycle determination.

Journal Club - Warming on chytrid infections in lake phytoplankton

To start this fall's journal club, I could not resist introducing my colleagues to the fantastic world of parasites... To fit the interests of my research group at LOG, I decided to present the work done by Frenken et al. (2016 Global Change Biology) on the role of water temperature on chytrid parasites epidemics in phytoplankton spring blooms.

Chytrids are fungi mostly infamous for contributing to the worldwide decline in amphibians. However, most chytrid species actually live in the oceans or in freshwater ecosystems, where they infect phytoplankton. Their life-cycle involves a free-living stage, the zoospore, which is infective to host cells to which is attaches in order to reproduce.

Using mesocosms, the authors investigated how 4°C rises in water temperature could influence phytoplankton spring bloom through its effects on one of its major factors of termination, chytrids. After introducing a range of organisms (including zooplankton, bacteria, phytoplankton and the parasites) filtered from pond water, they followed the plankton community over 4 months, including weekly samples of the phytoplankton community.

Their results indicate that warming affected chlorophyll-a concentration in the mesocosms so that values were generally higher in the control treatment reflecting regular temperatures, with a lower bloom maximum in the warm treatment. Earlier bloom termination in warm waters were associated with a more rapide increase in chytrid prevalence in the phytoplankton community. A rapide decline in prevalence was also found at warm temperatures to be associated with low host cell densities. However, this led to a longer persistence of the bloom and of the epidemic.

Changes in the water chemistry during the experiment also led the authors to question the effects of phosphorus limitation for chytrid epidemics, suggesting that high C:P ratio may have constrined the growth of the parasite. Importantly, their results also indicate that at warmer temperatures, zooplankters such as rotifers have an early development time and that under these circumstances, zooplankter population growth follows the rise of chytrid prevalence in the phytoplankton community. Because zoospores can be preyed upon by a number of organisms composing the zooplankton, it seems likely that these organisms used chytrid zoospore as an alternative food of resources at warm temperatures.

Overall, their results stress the need to understand the complex effects of global warming on phytoplankton bloom dynamics and emphasize the importance of considering parasites in such questions.





source for picture: http://cfb.unh.edu/phycokey/Choices/Anomalous_Items/fungi/Chytrid_05_500x317_on_Ast.jpg

Final DEVOTES Conference

Last week was held in Brussels the final DEVOTES conference. DEVOTES is a collaborative project that run from 2012 to 2016 with the overall goal of better understanding the relationships between pressures from human activities and climatic influences and their effects on marine ecosystems. Its leaders, Dr.Angel Borja and Dr. Maria C. Uyarra from the Marine Research Division of AZTI-Tecnalia in Pasaia, Spain coordinated the project to link its work to the management of European seas to reach and or maintain a “Good Environmental Status”. 

The programme reflected efforts to merge the worlds of managers and researchers by involving presentations from both stakeholders and scientists. Among the works presented during the event, the NEAT (Nested Environmental status Assessment Tool) software seems to break the boundaries between research and management of marine waters as it allows an assessment of biodiversity status and of GES across regional seas while also indicating the uncertainties related to the assessment. This tool has far reaching possibilities as it is not restricted to the EU Marine Strategy Framework Directive and can be used for other needs (e.g. national assessments). More about it here.

source for picture: http://www.azti.es/wp-content/uploads/2014/09/LOGO_DEVOTES_oscurecido-texto-copia.jpg