mercredi 16 novembre 2016

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

lundi 24 octobre 2016

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.




mardi 11 octobre 2016

EcApRHA: Applying an ecosystem approach to (sub) regional habitat assessments

The EU Marine Strategy Framework Directive (MSFD) has for main objective to achieve or maintain 'Good Environmental Status' (GES) in European Seas by 2020. The development of common criteria and methods during the first phase of implementation of the directive is essential to ensure consistency and comparability in the determination of GES and, hence, to guide policy makers in shaping future marine monitoring and assessment standards. To this end, a number of criteria and indicators have been notably identified to define GES on the species, population, habitat, and ecosystem levels. The biodiversity theme of MSFD gathers 4 descriptors (D& Biodiversity, D2 Non-indigenous species, D4 Food-webs, D6 Sea-floor integrity) with overlapping data requirements in biodiversity assessments, although the meaning of GES varies for each descriptor. However, MSFD implementation requires scientific and technical developments to conceptually frame biodiversity and to achieve meaningful monitoring and assessment of biodiversity.





The EcApRHA project is a 15 month project co-financed by the EU DG Environment running from December 2015-February 2017. It is co-financed by the EU DG Environment and will be implemented through collaboration of nine partners under the coordination of the OSPAR Secretariat (Convention for the Protection of the Marine Environment of the North-East Atlantic). 

EcApRHA focuses on overcoming challenges that are identified in the process to deliver regional biodiversity indicators for application of the MSFD for pelagic habitats, benthic habitats and foodwebs. These are challenges in access to and use of data, developing options for improved coordination of monitoring, how to construct regional indicators and undertake assessments of the indicators, as well as how these might fit together across scales and biodiversity components to work towards a more ecosystem approach.

The project aims to deliver:

- improved habitat and food web indicators to contribute to the Intermediate Assessment in 2017. This OSPAR assessment will be acommon regional report for relevant EU Member States to use in their national reporting on the state of the marine environment in their waters under the MSFD; 

- an Action Plan, recommending the steps to be taken by Contracting Parties to address the identified gaps and shortcomings to enable to achieve an ecosystem approach for (sub)regionally coherent habitat assessment.








vendredi 23 septembre 2016

EcApRHA Project: Ecological Approach to (sub) Regional Habitat Assessments

Two weeks ago, we were meeting with fellow researchers, OSPAR secretariat and with policy makers in London for the 3rd EcApRHA meeting.

During the round tables, we discussed progress on the development of indicators of the 'Good Environmental Status' for North-East Atlantic regions under the EU Marine Strategy Framework Directive.

Things keep being quite hectic but I'll write more about this in the future.

More about the meeting here: http://www.ospar.org/news/ecaprha-first-wp4-ecosystem-perspective-workshop 




Source for picture: http://www.ospar.org



And a picture of the afterwork dinner...







samedi 26 mars 2016

In the top 10 best peer reviewers for Peerage of Science!

Peerage of Science is a free service for scientific peer review and publishing founded in 2011 by Finnish ecologists Janne Kotiaho, Mikko Mönkkönen, and Janne-Tuomas Seppänen. One of its main purposes is to develop the practice and the evaluation of science.

Anyone having produced a publication as first author can become a peer and review the submitted manuscripts. Peer-reviews are evaluated among reviewers, giving more or less weight on some of the reviewers' suggestions to the manuscript.



In order to further promote the interests of the researchers registered as users of the company’s services, Peerage of Science awards every year The Reviewer Prize, to the best peer reviewer of the preceding year, as determined by performance judged by the evaluation of peer reviews.

Halfway to the final ranking, I had the surprised to be notified by Janne-Tuomas that I made it into the top 10! A nice surprise that adds to the experience I gained in this new reviewing experience. Let's see if I can keep up in the next 6 months :)


More about Peerage of Science here and here.



Source for picture: http://book.openingscience.org/images/novel_scholarly_journal_concepts_3.jpg

mardi 22 mars 2016

Parasite humour


Yes... I laughed.... And I am... Still... !


I have been traveling a bit and I still have to move out of my flat by March 31st, so no serious post this month ;)


Source: http://www.sadanduseless.com/2014/05/hipster-photo-revisions/

vendredi 5 février 2016

On stickleback fishing

Sticklebacks are trash-fish that anglers typically catch by mistake while targeting other fishes so why would you try catching some? The reasons are diverse and include:

-    Fish-keeping: the fish is easy to keep in tanks and males have bright breeding colours during the mating season (more here),
-    Consumption: stickleback are eaten in parts of Japan (order some here) and were fed to ducks and pigs in the Baltic countries in the 1800s (more here),
-    Oil extraction: Estonia notably used sticklebacks to produce fuel for oil lamps in the 1900s (more here),
-    Scientific research: sticklebacks have become an established model in biological sciences (see Barber 2010; Merilä 2013).

Fig. 1 We caught over 200 threespine stickleback with the seines this time
In the following parts of this article, I will focus on techniques to catch sticklebacks for fish-keeping and for scientific research because exploitation of stickleback is fairly rare nowadays. I will explain where and when to look for them, as well as the potential implications of using different methods to catch them.

Nota bene: stickleback vs. sticklebacks as plural forms...
It might be worth mentioning here that the plural form of "stickleback" can be found both with or without an "s" in the literature. There seems to be no clear rule concerning this matter. A native English speaker has told me a while ago to use "stickleback" as plural form when talking about several individuals of the same stickleback species and to use "sticklebacks" when talking about several species of stickleback (i.e. like "fish" vs. "fishes"). That's the rule I use but I admit that other forms might just be as correct. I also take this opportunity to mention that  - if we take the exemple of the threespine stickleback - "threespine", "threespined" and "three-spined" are used and that, again, there seems to be no right or wrong form. I just prefer the shortest version.
 
Fig. 2 Breeding threespine stickleback (gravid female on the top and male with breeding colourations at the bottom) and phylogeny of sticklebacks (modified from Barber 2013)


Where and when to find sticklebacks?

Sticklebacks have a holarctic distribution, i.e. they occur in the northern hemisphere. If we want to go into details, the answer will depends on which species of stickleback we consider. Most of the time, we refer to the threespine stickleback (Gasterosteus aculeatus) but tremendous work has been realised on other species, especially on the ninespine stickleback (Pungitius pungitius) (see Fig. 3). Accordingly, most of the following discussion will concern these two species.
Fig. 3 Threespine vs. ninespine sticklebacks

The threespine and the ninespine sticklebacks are marine species that have repeatedly colonised fresh and brackish waters during glaciation events of the Holocene. Accordingly, they can be found in coastal waters but also in lakes, ponds and rather slow-flowing rivers and streams. It is important to mention here that the distribution of the ninespine stickleback is more constrained to higher latitudes compared to that of the threespine stickleback.
Fig. 4 Breeding behaviour of the
threespine stickleback

In large water bodies, stickleback can be found in shoals within 5m to the surface. Like most fish, the colder the water becomes, the deeper (i.e. where the water is the warmest) the fish should be found. In the sea, many populations are anadromous (i.e. the live in the sea but breed in brackish of freshwaters). During the breeding season, individuals gather at 1-2m deep grounds (almost any substrate might suit as long as a bit of aquatic plants are around. Males establish small territories where they build a nest (by gluing pieces of aquatic plants and sand with a secretion they produce - the spiggin glue), courtship females and take care of the offspring (see Fig. 4). This is most likely the time during which the fish (especially the males) are the most vulnerable and easy to catch.

Typically, individuals will gather but only after a few weeks males will establish territories and express breeding colourations. The breeding season occurs in the spring and in the summer but specifying periods depends on the population. In Southern Finland for instance, threespine stickleback gather in early May at the grounds, actively breed in mid-June and stop reproducing around mid-July. During the breeding season, a few immatures that hatched on the previous year can be found but will not breed. After females lay their eggs, they usually leave the breeding ground to open waters. Accordingly, the (operational) sex-ratio will become more and more male-biased during the season. At the end of the breeding season, dying males, exhausted by their investment into reproduction, can be found in the water. The fry can generally be found on the breeding grounds at the end of the breeding and a few weeks after.


Which technique?

Different techniques can be used to catch sticklebacks and can be gathered in three main categories:

-    Angling: you can catch stickleback by using a simple line with a piece of earth worm, a bloodworm or maggot. It is the basic leisure fishing. Although it gives you the opportunity to have a beer while fishing, it is usually not an efficient way to catch a lot of stickleback.
Fig. 5 Seine fishing

-    Netting: two types of nets (more here) are used when fishing for sticklebacks. 1) Cast nets are circular nets with weights attached to its edge. It is thrown so that it spreads out and sinks in the water and the fish are caught by hauling the net back. It has the advantage that it can be used alone almost everywhere. However they are typically small, the casted net can scare the fish away and the animals might also escape by the time it actually sinks. Accordingly, it is rather used when fish are in shallow waters or at the top of the water column 2) Seining is the most common netting technique used to catch sticklebacks (see Fig. 5). The seines  hang vertically in the water thanks to floaters on the top edge and weights on the bottom edge. In contrary to cast nets, it cannot be used alone and require two fishermen to hold the side edges (unless you use a boat). For small seines, fish are caught by walking the net in the water, closing it quickly and rising the bottom edge. For both types of nets,  the mesh size of your trap should be smaller than the mean width of the target fish.

Fig. 6 Minnow traps can be used in almost any situation
-    Trapping: different kinds of traps exist (more here) but the most widely used are minnow-traps (i.e. basic bottle traps) and related traps. Minnow traps (see Fig. 6) are likely the most widely used traps to catch sticklebacks because they do not require spending much time catching the fish, they are easy to transport/carry (some models can be quite light and folded), and they can be used for virtually any type of environment (beware that heavy/metal-made traps might however get stuck in muddy bottoms, which can be a problem for deep spots). They can even be easily built from empty plastic bottles (see this). Again, according to the size of the targeted fish, different mesh sizes should be considered. However, it requires to stay for a while in the water and, in general, cannot contain many fish due to their typical small size (but big versions do exists and can collect loads of fish).


Your choice on the method will depend on:

- the place where you catch the fish from (e.g. if you can wade at the site, you can use seine nets but you may prefer traps if you cannot),
- if you are alone or not (alone: traps or cast nets; not alone: almost anything),
- the time you can spend catching fish (if you can only spend little time per day, use traps but that can involve several visits over a few days to get enough fish; if you can spend a day fishing, use seines).
Fig. 7 I had great catches with this kind of minnow-traps


To date, the most efficient kind of trap I’ve seen (but rarely used) for any stickleback is made of transparent plastic with removable entrance/mouth pieces. I could not find a picture online (and I have no photo) so here is a quick drawing to give you an idea (see Fig. 7).


 
Recently, research has been carried on the use of these traps in stickleback research. Two main aspects have been investigated: the roles of baiting, visual attractors and of trap type on catches.

Smelly baits and shiny objects, supposed to either mimic bait fish (possibly conspecifics for gregarious fishes) or just to trigger curiosity,  are typically used to attract fish to the trap. Some models of minnow traps have a compartment to place baits that can help attracting the fish and pieces of aluminum fold can always be attached to the meshes. In a series of studies, Merilä (2012, 2015a and 2015b) investigated how baiting and attractors might affect catch per unit effort of sticklebacks. He found that baiting with blue cheese increased the amount of catches of ninespine stickleback but not of threespine stickleback. Shiny attractors (i.e. pieces of aluminum fold) did not improved catches for both species.

Importantly, these studies revealed large differences in catches success among different minnow trap models, including closely similar models. More recently, we coupled field observations with laboratory experiments to determine if the traps differed in their abilities to attract threespine stickleback or to keep them trapped (Budria et al. 2015). We notably found that two very similar trap models differing mainly incolour (metallic vs. black) deeply affected the escape rate of the fish during the experiment (metallic was the best). By comparing trapping success in field and lab conditions, we also found that both attraction to the trap and escape rates affected trapping success. If some stickleback were more likely to be attracted to some traps rather than others, this might have deep consequences for laboratory studies as the sampled fish might not be representative of the whole population. Further work is thus needed to consider this issue.


First steps to keep your fish alive
Fig. 8 Air pumps are needed when transporting live-fish over long distances.

Once you have your fish, what are the first steps to keep them alive? During a long or warm fishing party, you can keep them in a bucket (if possible at the shadow during warm days - placing some leafs to float at the top of the water might be enough). They can remain like this for short trips but if you plan on fishing for a while or on taking the fish for a long trip, placing the them in a keep net or adding an air pump to the bucket is advised (see Fig. 8). You can also put the fish in a cooling box on warm days. Once you reach home or the lab, avoid placing directly the fish in new water to avoid any stress due to high changes in temperature or pH, et voilà!


Bonus for reaching the end of this article

A rare beauty: a fifteenspine stickleback we caught from the shore of Nauvo, Finland, in 2011.

Sources for pictures:
http://www.cell.com/cms/attachment/2009177165/2031548694/gr1b1.jpg
http://www2.dnr.cornell.edu/cek7/nyfish/Gasterosteidae/threespine_stickleback.jpg
http://www.maine.gov/ifw/fishing/species/identification/images/ninespinestickleback.jpg
http://image.slidesharecdn.com/63ch51behavior2005-130827153304-phpapp02/95/63-ch51behavior2005-7-638.jpg?cb=1377617655
https://en.wikipedia.org/wiki/Seine_fishing#/media/File:Seine_%28PSF%29.png
https://www.clarku.edu/departments/biology/fosterbaker/images/john_trap.jpg


vendredi 29 janvier 2016

Parasite of the month

Freshwater mussels Lampsilis spp.


Mussels of the genus Lampsilis  are widespread in North American streams. While the adult has a typical filtering life-style, the first larval stage - the glochidium - is a microscopic parasite of freshwater fishes. Young mussels attach to the gills of the fish host with their shell and suck their blood until they become large enough to move to the bottom of the stream.
The fascinating part of Lampsilis life-cycle is how they can reach the fish host. Indeed, the adults are typically sessile, they evolved a strategy to attract the fish host to increase transmission rate of the young mussels: like anglers, these mussels "fish" to get close to the host.

In these shellfishes, the mantle evolved to look like a prey fish of the host. The mimicry is improved by the contractions of the mantle that imitate the tail movements of the mimicked prey. When hungry host fish get to bite on the lure, the adult mussel ejects in its mouth hundreds of glochidia that attach to the gills as showed on this video:


Actually, several mussel species have evolved comparable life-cycles, with glochidia being more or less specialists towards certain kinds of host fish. This has led scientists to hypothesize that the composition of mussel communities might to some extent be dependent on the composition of the fish community. By using data on the occurrence of several mussel and fish species in the Great Lakes, Schwald et al. (2012 Diversity and Distribution) evidenced such pattern. Their analysis revealed that host fish presence was the strongest predictor of mussel occurrence. The study notably indicates that watershed identity also explained a large proportion of mussel species composition, highlighting the importance of the history of invasion phenomenon.