Sedimentation rates using tube sediment traps only collects sediment falling from above (sediment deposition), but does not account for sediments being suspended at low heights from the bottom, which occurs very frequently and are not trapped by the elevated collector tubes. Also, sediments act producing abrassion on coral through horizontal displacement close to the bottom, and are not fully trapped by collector tubes. Another way of sediemt action is masive sediment horizontal displacement that partially or fully bury or harm corals during storms. For that reason I think that the proposed proxy (percent of number of coral colonies belonging to sediment resitant species) is more representative and integrative of the ways that sediments as whole can damage corals, versus using vertical sediment deposition traps. Additionally, use of sediment traps require very repetitive sampling and thus does not allow to be applied in extensive coral areas. I think that the solution is to use the proxy mentioned in my question. Yes or no? Could this proxy be applied in multivariate analyses, BIOENV of PRIMER, for example?
Using species composition as an indicator would be most meaningful if you have reasonable background, control or transact data showing a relationship between sediment load (and/or other stressors under consideration) and the composition. Community structure can be responding to a variety of biophysical or geochemical gradients so you'd want to be sure your experimental design challenged the relationship. I'm no coral scientist but this is what I look for in such an indicator use in other situations.
Dear Pedro Alcolado,
Reinhold Leinfelder published some papers about corals in environments with a strong terrigen sediment imput:
https://www.researchgate.net/publication/230799470_Could_Ecosystem_Atavisms_Help_Reefs_to_Adapt_to_the_Anthropocene_
https://www.researchgate.net/publication/258767280_Assessing_the_ecological_effects_of_human_impacts_on_coral_reefs_in_Bocas_del_Toro_Panama
https://www.researchgate.net/publication/259981048_Importance_of_heterotrophic_adaptations_of_corals_to_maintain_energy_reserves
https://www.researchgate.net/publication/265216168_Pathways_towards_superoligotrophy_in_tropical_scleractinian_coral_reefs_-_a_Jurassic_perspective_and_a_modern_Jurassic-type_reef_setting
https://www.researchgate.net/publication/265216132_Reefs_and_Carbonate_Platforms_in_a_mixed_carbonate-siliciclastic_setting._Examples_from_the_Upper_Jurassic_%28Kimmeridgian_to_Tithonian%29_of_West-Central_Portugal
Reinhold Leinfelder is also at Researchgate:
https://www.researchgate.net/profile/Reinhold_Leinfelder
Perhaps he can tell you how he thinks about your idea from his perspective based on his research of extant reefs in Panama and fossil reefs around the globe.
I hope this answer, or least some of he links I posted prove useful to you.
Conference Paper Could ‘Ecosystem Atavisms’ Help Reefs to Adapt to the Anthropocene ?
Article Assessing the ecological effects of human impacts on coral r...
Conference Paper Importance of heterotrophic adaptations of corals to maintai...
Conference Paper Pathways towards superoligotrophy in tropical scleractinian ...
Conference Paper Reefs and Carbonate Platforms in a mixed carbonate-silicicla...
In terms of multivariate analysis, are you suggesting that species relative abundance be the variables? You could perform something like NMDS on species abundance, and use R functions such as envfit() and adonis() (I believe both are in the vegan package, but I'd have to check) to perform correlations with environmental variables (sediment load, for ex) and MANOVA. However, I think you would require some measure of sedimentation to make any compelling arguments, at least initially.
Dear Daniel and others,. Thank you for your answer.
What I need is specificallyto use de total percentage in number of coral colonies of species that has been proved to be very resistant to sediments in all the different way that such sediments can affect corals (deposition, abrasion, burying). It would be a proxy (substitutive) indicator of sediment damage to coral communities. Examples of such species resistant to sediment are Siderastrea siderea, S. radians, Porites astreiodies, etc. I am not meaning community structure, but a percentage of resistant corals in a community structure.
The use or sediment traps only allows to measure deposition component and has to be used repeatedly to cover the variation in time of sediment action among months, years, after unpredictable storms and hurricanes, sudden river outflows, etc. It is also too expensive and time consuming.
For that reason I do not like to use sediment traps. I am dealing with coral reef ecology research in several sites around Cuba; thus I need a fast effective method that integrates al the ways sediments can affect coral reefs.. Could I use this integrated proxy indicator based upon total percent of resistant coral pecies to represent averaga sediment impactn on coral communitiy sites around Cuba, in oreder tor applyi BIOENV of PRIMER software, for example? It has been a missing factor in my current coral reef research and condition assessments, nd determining the all involved factors.
Pedro,
I understand what you're getting at. Many multivariate techniques are exploratory, and may not provide you with good predictive power (some may disagree with me there). What a multivariate ordination technique could do is show differentiation of coral communities according to species composition - and you can draw conclusions regarding the physical characteristics of those reefs. You could also try linear discriminant analysis, using apriori groups (possibly sediment-related groups, LOW, MEDIUM, HIGH, etc...). You could then use the LDA to predict group (sediment condition) of an unclassified reef based on species composition.
That's about all I can think of without knowing what you want to end up with. Good luck!
Sorry Daniel and others, but I think you did not understood me maybe because I was not clear enough. I am not dealing specifically with multivariate analyses, but with a possible indicator proxy of sediment impact, using the total sum of the percentages of numbers or sediment resistant coral species to indicate sediment impact on the coral community. The higher the percentage the higher sediment impact to the reef is inferred. I have not received yet an answer about that. Could be this proxy it be a good quantitative indicator (% of resistant coral colonies) of sediment impact on coral communities? I do not care now about what multivariate analysis I would select; there are some to select, like BIOENV, for example. Please read carefully my questions and I will appreciate very much a relevant answer. Sorry for burdening so much.
Best wishes,
Pedro
Alternatively you could measure the siltation using a SediMeter, which measures both suspended load (near-bed turbidity) and sediment accumulation (bottom level), and it's even useful for detecting bedload transport. See lindorm.com
Thank you for the many unvaluable recommendations. But what I need is to sample extensively many reef sites around Cuba using an iincator as simple, cheaper and less time consuming as possible. For that reason sediment traps seems to me non.practical (time consuming, needed repetition of using of traps at each one of the tens of reef sites, and expensive). I need a most practical and fast indicator. For doing that I want to to calculate the total percent of well recognized sediment resistant species as an indicator. So, what I need is to be surer about which are really the most sediment resistant Caribbean species. In other words a simple fast, easy, less time consuming and less repetition effort, I have ellaborated such list from published papers and my own experience, but would appreciate support from other specialists to be as much sure possible about really considering good indicative species for the purpose of summing their percentages. This total persentage in a reef site wolud give a practical criterion to compare sediment stress (including sediment fall from above and from resuspension form the bottom, burial, abrassion) on coral communities around Cuba. For that reason I ask about whicht coral species are considered as most sediment resistant. Then I could use these total percentage of resistant species at each reef site to apply mutivariate analyses, for example.
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