Aquatic Ecology - Science topic

Bonjour,

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To statistically compare Shannon-Wiener index values between two years:

By following these steps, you can effectively compare Shannon-Wiener index values between two different years in a statistically rigorous manner.

By the laws of statistics, no crime, it is allowed.

Aquatic insects play several functional roles in nutrient cycling within urban streams:Detritivores: Many aquatic insects feed on organic matter, such as leaves and wood, breaking them down into smaller particles. This process releases nutrients like nitrogen and phosphorus into the water, making them available for uptake by plants and other organisms.Bioturbation: Insects like burrowing mayfly larvae and caddisfly larvae disturb the substrate as they feed and move around, which enhances the mixing of nutrients and oxygen in the sediment and water column.Nutrient Transformation: Aquatic insects can transform nutrients through their metabolic processes. For example, they may convert organic nitrogen into ammonia or nitrate through excretion, contributing to nutrient cycling.Predation and Grazing: Insects that feed on algae or other small organisms regulate their populations, indirectly influencing nutrient dynamics by affecting the growth and composition of algal communities.Respiration and Decomposition: Like all organisms, aquatic insects respire, releasing carbon dioxide into the water. Upon death, their bodies decompose, releasing nutrients back into the ecosystem.Habitat Modification: Some aquatic insects construct shelters or modify the physical structure of the stream habitat, creating microhabitats that can influence nutrient availability and cycling for other organisms.

Dear Vahin,

If I may develop and clarify the context a little further:

1. With all due respect to the authors, that are recognized pioneers in the field, the article you mentioned is over 15 years old. The SDM calibration and evaluation design has tremendously changed since then, and several biases have been shown in previously admitted best practices.

2. Please be aware that evaluation metrics such as AUC and TSS have been recently shown to be biased by prevalence (see Somodi et al. 2017; Leroy et al. 2018). In other words, for low prevalence species (i.e., rare species), such metrics largely overestimate the quality of the predictions, and do not reflect the true. Therefore, prior studies and evaluation metrics must be taken with care and knowledge of this evaluation metric limitation, especially for extreme prevalence cases.

3. Although the question is targeted towards Maxent, it is one algorithm among others. It might perform a little better with low sample size. However, for such small sample size it becomes more a model/evaluation design than a Maxent problem.

Having said that, you can still run Maxent, or any other algorithm on your dataset. However, I would recommend a calibration and evaluation design that corresponds to the current standards which means:

- An N-fold cross-validation, with spatial blocks to address autocorrelation issues if possible.

- A projection uncertainty, either using the same N-folds, bootstrapping or any other resample techniques.

- A model evaluation metric independent of prevalence (because you are in an extreme prevalence case), such as the Continuous Boyce Index.

In addition to that, or alternatively, a NULL model approach is also a good solution. The idea is to estimate how much better your model is, compared to a model trained on the mean of the observations. If it is not significantly better, you can use the mean of the observations instead.

The reason for these 30 to 50 observation thresholds that was mentioned by others, is that lower sampling sizes usually do not pass such up-to-date quality checks, or produce projections that are too uncertain to conclude.

I hope this helps and give you hints towards the appropriate litterature. Of course each case is different, but you must be aware of the current best practices and remaining limitations in SDMs for not producing false positive outputs :-)

Best regards,

Alexandre

You are most welcome dear

Dr. Geddada Mohan Narasimha Rao . Wish you the best always.

@all Apologies for the confusion in my previous response. You are correct that Thalassiosira weissflogii diatoms typically produce a brown color tint in the water rather than a green color. I apologize for the oversight in my previous explanation.

In the context of shrimp larval rearing tanks, the presence of a green color in the water is more commonly associated with the overgrowth of green algae, such as species from the genera Chlorella, Nannochloropsis, or Tetraselmis. These green algae can proliferate under favorable conditions and lead to the water turning green.

Excessive green algae growth can have various impacts on the larval rearing tank and the shrimp post-larvae (PL). While green algae themselves are not usually directly harmful to shrimp larvae, their overgrowth can indirectly affect the larvae and potentially lead to high mortality rates. Here are some possible reasons for the negative effects:

To prevent or manage excessive green algae growth and mitigate potential risks to the shrimp larvae, you can consider the following measures:

By maintaining optimal water conditions and preventing the overgrowth of green algae, you can help reduce stress on the shrimp post-larvae and minimize potential mortality rates.

This is indeed a general problem, not limited to AAS. Several recommendations (and even books) dealt with this topic, among them the classical reference of the Analytical Methods Committee. (1987).

A CI of 95% means that 95% of the values are within the interval. These are statistics, maybe this can help? https://en.wikipedia.org/wiki/Confidence_interval

Yes, I would not accept just one reviewer. Some journals have up to four! But two is perfect :)

J. C. Tarafdar Thank you, but this publication contains no reports on B12 levels in aquatic ecosystems.

The role of volcanic activity as a significant factor contributing to ice melt still awaits a confirmation. For some further details please kindly consult the following site:

Check out Qiagen

Hi !

If you get satisfactory results after checking the blank filters, you can use the scraping method for d15N. Just scrape off the layer of filter paper from behind without disturbing the top layer (avoid any contamination while doing so). For d13C, use a part of filter paper if the content is too high after acid fumigation.

Hope this helps !

Prachi

Laura Dzelzkaleja Thank you for responding. I have tried so many grouping methods, from spin-glass and random-walk algorithms, to clustering co-occurrence matrix and clustering presence-absence matrix. The most simplest solution presence-absence matrix seems to work "best". I have also seen people clustering positions of species within multivariate species (e.g. CCA). This often results in large number of groups, but these cannot be clearly discriminate/predicted. Additionally, the later one this circle reasoning since you first group species in the dataset based on the predictors and then try the predict them based on the same predictors. Also, everything is correlated with everything, which is not necessarily a big issue for the models, but more for the interpretation. For the last point I have not yet found a meaningful solution.

Of all the ones I've used before (Leica, Zeiss, and Olympus), the Olympus CX31 has never failed me in terms of getting good quality images of marine invertebrate larvae, copepods and even ciliates. As far as I know the CX31 has been discontinued and they've rolled out a new model: CX43/CX33 - which is of course more expensive than the last. For pictures the CX31 is modular which allows for a camera attachment. Leica is the go too if you have the funds, they have amazing imaging software that allows you to create composite images from different views of the specimen.

Hope that helps!

Yes, the null hypothesis in RELATE is that the correlation is zero. As you have a lot of samples you have a lot of statistical power to detect departure from the null. The significance tells you how likely it is that you would observe a value as high (or higher) than the value you have observed if the true correlation was actually zero.

There are many other tools in Primer you could also try (RELATE for 2-way designs, BIO-ENV, etc.), depending on your survey design. It might be that you get more meaningful results if you combine samples, maybe pooling nearby samples for example. It is likely, given that you have so many samples, that the signal (from the environment) is being lost in the noise (many samples each dominated by one or two species of fish).

Yang Liangfeng (Naning Agricultural University) and John Morse (Clemson University) published a book with keys on the aquatic macroinvertebrates of China for water quality. This publication already mentioned is in both Chinese and English editions. Author: John C.More & Yang Lianfang & Tian Lixin Language: English ISBN/ISSN: 7563002405 Published on: 1994-01 Paperback

Probably eutrophication caused by the sewage discharge from cities can be one of the reason for yellowish-green color of costal water near cities .

Body coloration in many poikilothermic animals is plastic and can be adjusted at the individual level. Particularly in fish, this rapid change is called physiological color change and refers to synchronous movement of pigment organelles within pigmented cells in the skin called chromatophores (black melanophores containing melanin, yellow xantophores containing pteridine, red erythrophores containing carotenoids, and the more rare blue cyanophores containing an unknown cyan biochrome), as well as in changes in angles of light reflecting crystals in iridophores and leucophores . When aggregating the dark melanosomes of the melanophores, the skin not only becomes pale but also more transparent. Increased body transparency can also aid background matching.

The advantage of rapid color change is obvious, because it allows rapid adjustments and flexibility at the individual level depending of the situation. It is used for background matching as well as for communication and sexual display . Studies on pipefish have shown that the color ornaments of the females are shut off if a predator enters the mating area, clearly indicating the advantage of an adjustable body appearance and the risk of a colorful display .

Dear, sorry for the delay in responding; unfortunately we do not have a better photo, and by mistake the otolith was not saved. Best regards.

Hi Li Chen.

He considered that James Des Lauriers is right in what he raises; fishing for any shark species should be restricted and regulated, even if not in danger. It should be analyzed that only intensive fishing is not the only factor leading to the danger of extinction of certain shark species; we must also consider climate change and ocean pollution. Set of factors that in a relatively short time can dramatically reduce shark populations in the world.

Similar question:

Concrete is often hyped as "chemically inert". But in my experience, new concrete leaches alkaline solutes in low concentrations that get lower over time. I used new concrete paving stones as substrates for a disturbance experiment in streams. I realized from the soapy sensation on my hands that there was a chemical effect. So I let them leach for six weeks before starting the experiment.

My samples included midges, a diverse set of mites, caddisflies, beetles, and mayflies. The river lacked stoneflies in any appreciable numbers so I was not surprised at their absence on concrete. So, I believe that the chemical effect would be very minor, short lived, and probably negligible in established flumes..

The physical effect would be more interesting and permanent. A flume is so uniform as to attract only certain species fond of those conditions. If you have replicate flumes.....seems like an opportunity. Add physical structure to some and not to controls: coarse woody debris; cobbles; boulders....see who moves in and write that paper.

Good luck in all your work.

Declan

Aaron Baxter has published on diamondback terrapins in estuaries of Texas :

google his names and terrapins for several pdf reports of his studies. Best, PZimba

apply in wwf

I should add. It would seem that this snail could be considered to be a cryptogenic species as it was first found in Ireland in the late1800s. Its distribution follows that of an expansion from Belfast and Dublin westwards. So it is very likely to be a human introduction. However, look at Baker (1945) The Molluscan Family Planorbidae. He discusses the spread of this genus through a Caribbean Island chain. This implicates birds in dispersal. In the case for Ireland one wonders why if it was found only from the 1890s (and is a conspicuous species) why did birds not transfer this snail beforehand since the last glaciation. So while not absolutely certain to have been introduced to this island by humans, it would seem to be the case. The Biodiversity Ireland www has a distribution and to this there are further records I have found on the Shannon, which I indicated earlier. Dan

SIMPER is used after the differences between factors are confirmed using an ANOSIM or PERMANOVA test, the factors sometimes or frequently are defined a priori (before to start the research or analysis) according to some geographical, physics or chemistry characteristics that show an effect on the community as a driver of its structure. If there is not a clear effect for any factor selected a priori SIMPROF test allows to observe groups with significant differences, without significant differences SIMPER analysis has no sense.

Hello James Des Launriers, I fear you may be wrong to say that there are 'more people that the earth can support', because the earth may not be able to support even a single greedy!

I think, the greed and selfishness of the powerful individualist minority (both in the poor and rich countries) is responsible for the mess on the earth!

The pathetic fate of ignorant people in the poor populous countries is not the sufficient reason to say that excess of population is the main problem of the earthly mess there or the less population size in the developed world is the reason for the environmental care or cleanliness found in such societies!

Mahatma Gandhi once truly said "the earth has enough resources to meet everybody's need, but not enough to meet anybody's greed"

Agricultural analysis of food production says " five kilogram of grains are required to make a kilogram of meet!"

So if people had led a simple life style, the soils should not have been so intensively manipulated to not only of its utter degradation, but that of water, air, food and all of the environmental components!

In the above context, there is a challenge in the philosophy for humans to find a wise answer to certain significant questions: 'Why don't people change their faulty lifestyle?' 'Why don't people care the needy?', Why don't people worry about future generations?' and the like.

If people properly understood ecological philosophy, they would have changed their attitudes and found reasonable answers to the above questions and would have solved the environmental crisis!

Rather, people want to keep away such ecosophical questions from science as 'spiritual' matters!

The challenge of ecology is to reasonably equip people to bother about the ecological basis of the same and to find out true answers to such questions!

Ecology is a moral science too! Ecology enables humans to find answers to the ultimate of good and bad in all individual actions on the earth!

Eco-spirituality is a scientific theme that require proper scientific attention, rational analysis and criticism!

It doesn't happen, because the irrational individualist who rule the current world always ignorantly behave as if "to be in darkness is so easy, but to get exposed in light is difficult and painful an experience" that prompt them to sacrifice the existing physical comforts!

Hi Mark

I agree in large part with Andrew: Certainly use the raw data rather than converting to a percentage. Variability is expected; ANOVA accounts for that. I would add that you can simply test for normality to confirm that each of your three groups is normally distributed. If you learn that your data are not normally distributed then you can try some transformations to make them normal....that usually works; same transformation for each group. Then proceed with your ANOVA adding trial as a factor in the ANOVA thus accounting for fussy predators. If it's well replicated and the effect is real....you should be able to detect it.

Have fun!

Declan

Hi.can any one present for me the pdf reference about theory and scale for philanthropy in psychological perspective

Hi Libourn,

The Indval Package is used in R plataform. Then you will dowloading this package in R and just follow the instructions described by Pierre Legendre.

Levan Mumladze try this one http://chng.it/4KMsV5KbSw or

1. If you want to estimate biomass, regression equations are a good way to go. There are a number of equation sets out there: Benke et al 1999 and Burgherr and Meyer 1997 are good broad scale data sets. When using equations be sure to use the appropriate value for the intercept (typically denoted a). Sometimes ln(a) is reported as "a" - ln(a) will be -4.0 or so and a will be 1.0x10^-6 or so. They will get you to the same number in the end, but you need to be sure you use the right equation form. I would be hesitant to try and develop your own L-W regressions from those samples for the reason provided by .

2. I would still advise getting some dry weights so you can validate that the regression equations you are using are providing a 'reasonable' estimate. The masses will be off since they are preserved in ethanol, but they won't be wildly off. An L-W equation that under-predicts the mass of preserved specimens by 50% is just as big of a problem as a poor estimate of density when you go to scale up to the community.

3. Propagate your error / uncertainty through the entire process - don't ignore the error terms in the published regression equations. Apart from the regression equations, you have uncertainty in multiple measurements that need to be integrated / propagated.

4. For getting the mass of the community, if you have many samples/sites (hundreds) to get through you, can use the approach suggested by Jim Junker . However, this can result in greater uncertainty about your estimate depending on the taxonomic level to which you are going and whether or not the taxa are semivoltine or multivoltine - if you have mostly univoltine species this is less of a concern.

5. If you have less than 100 sites / samples, to reduce uncertainty, I would suggest directly measuring all animals that you identify (unless they are all univoltine, in which case Lusha M Tronstad 's method is most efficient). A simple solution for measuring the length of all animals is to take a picture once they are taxonomically sorted. You can then use ImageJ to quickly measure lengths with high accuracy. If your dissecting scope is equipped with a camera, this is simple and you are probably already doing it. If you don't have that setup, you can use a flatbed scanner and put the animals into a container with a thin flat transparent bottom. I use transparency film glued to a frame. A 1200 DPI optical resolution scanner will give you more resolution than you could reasonably need (even for daphnia). A good quality used scanner can be found for less than $10 in the US.

6. Be sure to remove trichoptera from cases before measuring.

Also if applying equations across spatial gradients or from different parts of the world consider:

It depends on the isotopic baseline in your food web. Primary producers can have a very wide range of d15N, and if the predators specialise on grazers which in turn specialise on a low d15N source, their d15N can be very low as well.

Lucas, Hellinger transformation is meant to solve the issue of double absences when computing Euclidean-based ordination techniques (PCA, RDA). Thus, it is not appropriate for CCA. Now, in the context of indicator species, you have to ask yourself if transforming your data (Hellinger or otherwise) is meaningful, especially if same sampling effort is put into collecting species from each of the categories you want to find indicators for. Remember that the indicator value doesn't depend only on the relative abundance of the species among categories but also its relative frequency, and the fact that a species has much higher abundances than others in the system must have some ecological implications. Now, the indicator value of one species is independent from the value of the other species in the assemblage, thus transforming for the purpose of accounting for large differences in abundance has little use. If you apply Hellinger (the square root of the relative abundance among species within a sample) and then compute the indicator value (highest value among sites of the product of the relative abundance and relative frequency of a species within a site) you are no longer values independent among species. Hope this helps.

Hi Nathan, we have high DOC and highly colored waters here in Maine. DOC is both an acid and contributes to alkalinity. We tend to have alkalinity even below pH 5 where the carbonate system is exhausted. DOC makes are streams and lakes more acidic for a given alkalinity, but DOC also supplies acid neutralizing capacity when pH is below 5. DOC is negatively charged and attracts and binds cations. This make heavy metals and Aluminum less toxic. Because lakes are solar collectors and because DOC is digested by UV light, there is a lot of clearing of water color in lakes. Maine streams are often tea or even coffee colored while lakes can be crystal clear. This digestion process releases Al, Fe and phosporus, generates alkalinity (or was it acidity? any chemists out there?), and precipitates TP as aluminum and iron compounds. Ferrous iron binds P, but will release it during reducing conditions (such as low oxygen conditions in the winter). Aluminum does not do that and is a permanent loss of TP in the bottom of the lake. Fish and macroinvertebrates benefit from DOC when soils are acidic and Al is mobilized. Ionic Al is bound by the DOC and particulate (POC) forms. Episodic pH drops can release Al and put in back into the toxic form and can lead to fish kills. Macroinvertebrates may also be killed and will drift downstream. So for the most part DOC is natural, important, and helpful for wildlife. Climate change probably increases the decomposition of organic matter in soils, leading to more DOC export from watersheds.

Following

Dear Mr. Thajudeen,

The premiere enzyme responsible for fixation of dinitrogen to ammonia, the nitrogenase, is extremely sensitive to the presence of oxygen because of the degradative tendencies of oxygen towards the Fe-S co-factor of the enzyme. However, hot springs provide an ideal environment for diazotrophs or symbionts as the excess temperature ensures that the partial pressure of gaseous oxygen would be higher than the ambient atmosphere and generally results in outgasing of oxygen into the atmosphere and the water becomes hypoxic. This is effect is absolutely conducive for the nitrogenase to function. However, the temperature might prove to be a hindrance for the enzyme to perform optimally for which hot spring cyanobacteria or other microbes tend to synthesize excessive extracellular mucopolypeptides and other polymers. The dissolved carbonates in the alkaline hot springs serve as buffers to any pH swing, thereby protecting the enzyme.

At or near deep sea vents, nitrogen fixers encounter environments where the element with highest electron affinity is usually sulfur. And the absolute absence of free or dissolved oxygen in there immediate environments enable the nitrogen fixers to perform optimally. Production of methane, hydrogen sulfide, sulfur di-oxides farther bolster the situation of hypoxia. There are articles indicating that gaseous nitrogen is abundant in hydrothermal fluids and the environment itself is limited by fixed nitrogen. Hence thermophilic nitrogen fixers reduce N₂ to ammonia in the unsedimented deep-sea vent regions.

In very cold regions, like the polar climates, the nitrogen fixation do take place beneath the ice or permafrost, in peat bogs etc but at very slow rates. And in it very rare in arctic oceans since the cold ensures presence of excess dissolved oxygen in the water which is a big roadblock for the nitrogenase. The global nitrogen cycle is not balanced since in the arctic regions, nitrogen fixation hardly, if ever, occurs, apart from some limited coastal settings and the rate of microbial denitrification far outweighs the ammonification in high latitudes. The tropical regions are characterized by higher rates of nitrogen fixation within the euphotic depth followed by greater ammonia oxidation through Annamox in the lower reaches of the nitricline.

This is why if all the niches of the world were considered, nitrogen fixation concept would have been needed to be rewritten as a result of a paradigm shift. Hence, in terrestrial conditions nitrogen fixation may or may not occur in polar climates but in water it is truly a rarefied phenomenon and can only, theoretically/hypothetically take place in oxygen minima zones, which need research to corroborate.

Thanking you,

Dr. Abhishek Mukherjee

Hi

1. General remarks:

Research studies are usually carried out on sample of subjects rather than whole populations. The most challenging aspect of fieldwork is drawing a random sample from the target population to which the results of the study would be generalized. The key to a good sample is that it has to be typical of the population from which it is drawn. When the information from a sample is not typical of that in the population in a systematic way, we say that error has occurred. In actual practice, the task is so difficult that several types of errors, i.e. sampling error, non-sampling error, Response error, Processing error,…

In addition, the most important error is the Sampling error, which is statistically defined as the error caused by observing a sample instead of the whole population. The underlying principle that must be followed if we are to have any hope of making inferences from a sample to a population is that the sample be representative of that population.

2. A key way of achieving this is through the use of “randomization”. There several types of random samples, Some of which are: Simple Random Sampling, Stratified Random Sampling, Double-stage Random Sampling... Moreover, the most important sample is the simple random sample which is a sample selected in such a way that every possible sample of the same size is equally likely to be chosen. In order to reduce the sampling error, the simple random sample technique and a large sample size have to be developed.

3. Specific remarks:

The following factors are highly affected the sample size and need to be identified:

4. Then, the sample size can be estimated by,

Necessary Sample Size = (z-score or t-value)2 * StdDev*(1-StdDev) / (margin of error)2 .

Regards,

Zuhair

That would be great. Thanks!

Hi Iestin,

The attached papers should point you in the right direction.

Tomas

It seems to be a leaf of Ceratophyllum (possibly C. demersum).

I have no idea yet.Good question.....

Dear Keston and Fjdor,

thank you very much for your suggestions. These were really usefull. I will check both options (including VEC models).

Thank you very much

I caught one of these in Liberia I would say a Lycodon capucinus

Hi Tom, I have seen these refs, but this does help and I do appreciate your assistance on this. I. badionotus appear to be very patchy in distribution probably due to poor recruitment and low population levels. Their population decline due to high fishing pressure is concerning as they appear to be important reef sediment processors. Their presence in my systems looks to have a functional stabilizing influence on water chemistry. Thanks again for your help!

Such methodologies are widely used, but the resolution is poor. I spent several years doing a master's using fatty acid analysis to differentiate between food sources in Atlantic Tarpon in the early 2000's. It worked...sort of. Here's the thing, fatty acids in tissue are not just diet-related, they're biosynthesized and utilized at different rates based on physiological changes & stresses to the organism. The best paper at the time was produced by a lab in the far white north, and there was so much mathematical black magic used in the paper that few people who were doing the work at the time believed them.

Isotope work is even more vague than fatty acid analysis. Okay, as Sharon pointed out, sharks may feed in marine and freshwater biomes...but what does that really tell you? Not much! A gut-content study (they can be done non-lethally) can tell you what species are consumed specifically, rather than...over the last year or two the shark fed on saltwater and freshwater organisms. For example, gut content studies in Florida in the 1970's (I believe 1977) found that alligators were feeding on a variety of native fish, turtles, and mammals. The lab I worked in did a preliminary study in the mid-2000's on alligator diet using gut-content analysis and discovered that their diet had switched to 95% exotic fish species. Would an isotope study been able to catch the change? I'm not sure, but I know it's much cheaper and more accurate to have students sort through the stomach contents of an alligator to see what it ate compared to using fatty acids or isotopes to calculate a ratio. What are tiger sharks eating in SW Florida estuaries? Probably saltwater and freshwater organisms when they can get them. But the 8'1" tiger shark I examined had eaten saltwater catfish and batfish. That's more interesting than a vague trophic-level analysis.

Isotope and fatty acid analysis can be good tools IF you are only examining higher-level trophic interactions. If you want fine details, stick to the old, dirty, stinky, disgusting methods that work.

Thank you all of you

thank you very much

the first-one I know already, I will look for the second-one

hi

maurizio

Dear Stephen,

Please request the following ResearchGate member for identification.

Good luck

The best review article on "Nanoparticles in aquatic systems". I hope this review addresses most of your questions. Here is the link to access the paper.

I think it must be an experiment of 2 years.

Dear Lucas

Choosing the right multivariate analysis can be a bit painstaking. In general, it all depends on the preference of the investigator to choose their ordination analysis. Some use weight of the parameters and others eigenvalue. Having said that, not all ordination analyses can be used for every data. There are ways that you can figure out what ordination analysis best suit your data.

If you have CANOCO software then your life can be a bit easier. Fear not if you don’t. Simply use the open source program PAST which contain all the ordinations and many more multivariate analyses. It also has non-metric multidimensional scaling which some prefer over PCA if values are not linear.  

First thing first you need to figure out whether your data (i.e biological) are linear or unimodal or somewhere between. Best test to do this is to run a Detrended Correspondence Analysis (DCA) and look at axis 1 gradient length of ordinated species data. If this number is lower than 2 [SD] units, your data is linear. In this case the best ordination to compare your biological data with environmental data is a linear analysis, such as RDA (Redundancy analysis). If it is higher than 4 [SD] then you have a unimodal data and analyses such as CCA are the best fit for your data. If it is between 2 and 4 standard deviation [SD] units it is not clear whether a unimodal or linear response model best fit the data. In this case run two separate ordinations, both linear approaches RDA and unimodal approaches CCA. Whichever, method gives you higher variation on community data that methods best represent your data (i.e. correlation with environmental variables).

Make sure to perform Stepwise backwards elimination to find what environmental variable are best correlated with benthos community composition.

Hope this helps.

David,

Have a look at these paper:

I have  short section on bioerosion in the Ecology of Indonesian Seas that you may find of interest; see page 635.

Hope this helps.

Tomas

Dear Dr. Kani,

you can collect water samples from local pond and measuring the chlorophyll a content and determining the trophic level of that pond during different seasons. Also, assessing some physicochemical parameters to evaluate the water quality status. You may identify phytoplankton if there toxic species or detect the level of Microcystis in water samples.

comparing your data with pervious study on the same pond, if there. Detecting human activities near to the pond that may help you to interpret your final data.

Use canonical corresponds analysis (CCA) to get the correlation between all different detected data.

Good luck,

Sara Sayed

dear collegue

According to my experience, seeing the big difference of drift between the previous night and the next, I suspect two events:

- an sudden abnormal water release from some retention structure (dam etc.)

- a spillage of toxic substance during the night

Maybe you can check out these events

cheerio

Try to play with MG-RAST server and MetAMOS pipeline:

It looks like Catostomus sp

Tomer,

The depth of colonization within a reef matrix is light dependant for encrusting autotrophs, but for sessile encrusting heterotrophs it's probably the water flow, i.e. food supply, that would be the key limiting factor. So the depth of colonization within the reef matrix is complex and will depend on numerous factors. The two attached papers may be of some help to get you started.

Tomas

 Showing the damage caused by invasive species can educate and convince many people.

I work as technician in the conservation project LimnoPirineus (http://www.lifelimnopirineus.eu/en). We are removing invasive fish from eight high mountain lakes in the Pyrenees. After three years of work we are getting some nice results such as the recovering of the natural transparency and the increase of abundance or the natural recolonization of many species of amphibians, invertebrates and crustaceans.

I have experienced that showing these milestones to the local people and pupils in local schools and high schools is convincing most of the audience.

Also, I have to recognize that a few people is not convinced anyway. However, I can see a very good progress at community scale.

Pl send me pics preferably fresh one I will try to Identify it.

Dr.Gore 

yes, the processes are many. There is also the "natural" version through (constructed) wetlands. They can be compacted by chosing a good locally adapted version of microbes and macrophytes, but natural regeneration through the filtering capacity of soils and plants has also been used in multifunctional parks (water filtration and recreation). Unless space is very scarse, such solutions tend to be less costly, but require a different set of knowledges and competencies than more conventional treatment plants. In any event, it's worth analysing entire process cycles and explore whether substances which are particularly difficult/expensive to remove can be separately captured and processed. As a general rule, end of pipe solutions are much more costly than cycling (where "waste" at one step of the cycle can become a resource for another one), thus learning from nature.

.

This copepod is a  tiny  Cyclopoid . The identification requests  delicate dissection of  the legs with focus on  the differenciation  between the right  and left  4th or 5th leg  in male and female .From which habitat is the specimen ?

This link may help

 Hi Lewis - thanks for your suggestions. The Science Citation Index is included in our Web of Science search and we aren't limiting based on date so hopefully we've already taken advantage of those papers. Best, Micah

The low spire of this Monoplex parthenopeus, remember me the more eastern form "echo" from Taiwan and Japan. I have a similar specimen from Masqat (Oman).

Cordially, Gianluigi.