Plankton’s Perspective in Trophic Mismatching

This blog is set out slightly differently than the usual post. The paper I’m basing this off is a review and is written in three distinct blocks so I have imitated this in my post. Enjoy!

Plankton is one of the many groups of species which base their seasonal cycles on changes in their environment. These phenological changes could cause disruption in the local ecosystems due to the increasing temperatures especially if the species with changing timings are relied upon or rely on a different species. Climate change driven phenological changes in both Phytoplankton and zooplankton’s population has been reported in freshwater and marine ecosystems. This paper looks at the evidence, reviews what these changes could mean for the plankton communities and suggests what future studies should focus on.

What is the current evidence for the trophic mismatching in the plankton?

 The authors looked at a very specific collection of papers by searching through ISI Web of Knowledge. By only looking at the papers studying holoplankton, and no transient life cycles, the number of papers reviewed reduced significantly. The authors then reduced the number studies further by removing those which did not show a significant difference  between the two levels and the measures of species performance or abundance must be directly linked to the degree of synchrony between trophic levels. Many of these papers focused on the spring phytoplankton peak and zooplankton grazers (mostly represented as diatoms or estimates of the phytoplankton biomass). They found that the number of studies has not provided for trophic mismatching, and so does not support trophic mismatch within plankton.

 There was very little field evidence and it was biased towards the spring events and phytoplankton grazers, especially Daphnia. There are also few studies directly matching abundance or performance to phonological mismatching. The authors suggest a more specific and dedicated research to measure the importance, identifying the conditions that may promote/negate the effects and to demonstrate a link between mismatching and population/ ecosystem effects.

What does trophic mismatching mean for the plankton?

 Current understanding of plankton seasonal succession states that there’s feedback between the zooplankton and phytoplankton, any factor influencing the rates of population affects the balance between these two populations. The plankton-cladoceran interaction forms the basis of many studies which increase rapidly in response to the seasonal increase of phytoplankton. Rapid seasonal increases in population size/ and fecundity has been observed, in response to seasonal increases in response to the available phytoplankton recourse. This suggests that to some extent the seasonal timing of the zooplankton population development will be dependent on food recourses. For the grazer’s population increase, the phytoplankton’s abundance needs to exceed the threshold amount, which is the point at which there is enough food to allow the zooplankton to reproduce. In extreme cases resource driven increases in grazer populations could feed-back on to their resources and suppress the phytoplankton populations, and lead to the collapse bloom. Modellign studies  suggest that if the temperature continues to change, the consumer-resource cycle could alter, and thus influencing replication, development and grazing.

Future priorities for studies of trophic mismatch in plankton:

The phenology of resource limitation: there are a couple of assumptions there are that resource limitation prevents reproduction this needs evidence. Food threshold needs to be found, laboratory studies are critical for this There are currently discrepancies in the data between about whether Daphina as the herbivore is the only factor affecting the populations, or it has been suggested that the Daphnia population growth may also be partly supported by grazing. Important to state what food resources are and are used.

Food chains to food webs:  the studies reviewed adopted the linear food chain paradigm. However, to understand the consequences mismatching future studies should adopt a wider view of the community, adopt more of a food web based approach.  For example, the seasonal period of abundance of the phytoplankton consumed by cyclopoid nauplii might be affected by strong grazing pressure from co-existing Daphnia.

The complexity of copepods: very few studies directly examine the potential mismatching between copepods and their food resources.  To truly understand mismatching in copepods, it would be necessary to define multiple developmental stage-dependent food resource windows and examine shifts in their seasonality over the longer term. As a further complexity, the life cycles of copepods may also be interrupted by quiescence and diapause, which may cause lags between resource availability and copepod development.

Conclusions

The authors summarised that although trophic mismatch has been proposed as a mechanism in which climate change could affect, there is currently limited evidence for this occurrence and its impacts on ecosystems. Since the evidence is also biased towards spring blooms and a small number of organism groups, further studies should address this.   The authors believe that by recognising and incorporating the that exist between population development at different trophic levels and the context in which the changes occur.  I, however, believe that a wider range of papers needs to be examined.
 

Thackeray, Stephen J. "Mismatch revisited: what is trophic mismatching from the perspective of the plankton?." Journal of plankton research 34.12 (2012): 1001-1010.

 http://plankt.oxfordjournals.org/content/34/12/1001.short