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nitrogen and phosphorus uptake rates of different species from a coral reef community after a nutrient pulse

by:Top-In     2020-08-06
Land runoff after heavy rainfall can increase the nutrient concentration in the waters that cover the coral reefs, otherwise the nutrient levels in these waters will be low.
Field measurements during the runoff event showed a sharp increase in nitrate (75-fold), phosphate (31-fold)
Ammonium concentration (3-fold)
Waters on the rocks on the edge of curaço Island (
South Caribbean).
In order to understand how undersea coral reef organisms use this nutrient pulse, we determined the rate of ammonium, nitrate and phosphate absorption of a rich coral species-lawn algae, six kinds of large algae and two kinds of blue bacteria were found in a series of laboratory experiments.
The nutrient absorption rate of submarine functional groups is different.
Large, hairy algae.
, Lawn algae and submarine blue bacteria Lyngbya majuscula had the highest unit biomass uptake rate, while the unit biomass uptake rate of coral Madracis mirabilis was the lowest.
Combining the nutrient absorption rate with the biomass of each functional group on the reef, we estimate that, the ammonium and phosphate transported during the runoff process are mainly absorbed by lawn algae and two large algae-the spotted leaf ophora and Dictyota pulchella.
Our results support the assumption, which is usually presented but rarely tested, that lawn algae and opportunistic large algae mainly benefit from the nutrition provided to coral reefs.
The study was conducted in the spring (March-June)
On 2012 and 2013, the edge reef of the \"No. 0 buoy\" at the research site on the leeward side of curaço Island, southern Caribbean (12°7′29. 07″N, 68°58′22. 92″W; ).
The location of the study is about 500 m from the opening of the Bay of Piscadera (12°7′21. 42″N, 68°58′12. 52″W), a semi-
Closed and highly normal bays receive nutrients from emergency spills from coastal residents and sewage treatment plants.
During our study, we observed rainfall at buoy 0 approximately every second, whether on 2012 or 2013 (
The average rainfall is 4. 17u2009±u20090. 61 and 4. 64u2009±u20090. 70u2009mm 24u2009h (±s. e. m. ), respectively).
In a parallel study in Den Haan, based on light-sample measurements at depths of 5 and 20 m, the composition of the submarine community of buoy 0 was estimated.
In shallow waters (5u2009m depth)
The submarine community of No. 0 buoy is mainly composed of lawn algae (cover: 44%)
White Beach (28%)
Interspersed with blue bacteria mats on the sea floor (11%), hard corals (7%)
And large algae (6%; mainly ).
It is the richest coral species in these shallow waters with a total coverage of 2. 5%.
The blue bacteria seats are mainly, and spp. ;
We did not observe a cushion for the undersea eugenic algae at the site of the study.
In deep water (20u2009m depth)
Submarine communities composed of large algae (43%; mainly and ), hard corals (
17%, of which 1. 3% ), white sand (12%), turf algae (10%)
And the blue bacteria mat (9%).
Standing biomass (
G DW per meter in reef area)
The above species on coral reefs are calculated by increasing the coverage on coral reefs (i. e.
From Den Haan)
With the dry weight of its unit area, the \"area density \"(
Don\'t confuse population density with n m).
The density of the surface of the species is defined as the species whose dry weight is covered on the bottom surface of each meter, taking into account the month-
The structure of life on reefs and reefs.
In order to estimate the area density of each large algae, we took 25 samples (0. 25u2009m)
Patches of different sizes, spp. and .
Large algae are then collected from the sample side, manually cleaned from attached organisms and debris, and dried at 60 °c for at least 3 days to determine their dry weight.
After quantifying their coverage in the sample body using image j, a conversion factor associates the dry weight of the algae with its coverage in the photo
Four groups can be calculated.
By cutting 35 of the plastic bottles incubated in depth for 6 weeks from 5 weeks and 20 µm, a similar conversion factor for lawn algae was obtained (
For more information on how we collect lawn algae, please see the \"sea floor Biological Collection\" paragraph below).
Each piece is photographed to measure the lawn algae cover (
Similar to above)
After that, the algae on the lawn were scraped off the plastic and frozen
Freeze and dry in Scanvac CoolSafe-dryer (
Science B. Scala. V.
Yide, Netherlands)
Determine their dry weight.
After Jantzen, we multiply 1 by the dry weight of the lawn algae.
Considering that the actual coral reef surface is more complex on the terrain than the plastic strip where we sampled turf algae.
Blue bacterial pads and attached deposits were collected from 10 0 samples at 5 and 20 µm depths. 01 or 0.
04 u2009 m placed on the sand 100% blue algae cover, with a 50 ml Terumo syringe (
Turumo, Europe (Leuven, Belgium).
The blue bacteria are frozen.
Freeze and dry using Scanvac CoolSafe-
Use the air recycling chamber furnace to dry and burn at 450 °c for 4 hours (
Sulphur plastic, Linggu, United Kingdom)
Therefore, their face density can be calculated based on the weight difference between the original samples (
Blue bacteria with sediment particles)
And burn samples (
Only sediment particles).
Most of the blue bacteria on the No. 0 floating body sit on flat sandy deposits with simple two-dimensional structure.
To estimate the face density of hard corals, we first estimated the coverage of all major coral species at 5 and 20 m depths using CPCe, as described in the previous paragraph.
For each coral identified, we multiply its coverage percentage by 2-D to 3-
D conversion coefficient (
Table 2 of Holmes)
According to the morphology of the coral species of interest, the surface area of the coral reef per meter is obtained for each coral species.
Then we multiply the data by a species.
Specific surface area to biomass conversion coefficient provided by Hardt (see Table 5. 1 in Hardt)
Get the biomass of each species per metre reef.
Summarizing the biological morphology of all major coral species in buoy 0, the total coral biomass of coral reefs per meter was obtained.
Finally, in order to obtain the face density of all hard corals, we divided the total coral biomass per meter of coral reefs by the total coverage of all corals on the coral reefs.
The water is collected from depth of 5, 10 and 20 CUCM, about 10 cm above the reef slope, using 5.
3 liters of plexiglass test tubes.
Because previous measurements show that the dissolved nutrient concentration at buoy 0 is uniform on the upper 20 µm of the water column, we will go from 5, 10 and 20 µm depth
Subsequently, three water samples were extracted from mixed water (
Branch length about 5 cm)
Six kinds of large algae (spp. (
Only 5 m in depth), , (
Only 5 m in depth), (
Only 20 metres in depth), , (
Only 20 metres in depth))
Two Blue bacteria on the sea floor (spp. (
Only 5 m in depth)and )and turf algae.
Lawn algae are not collected directly from coral reefs because scraping them off the surface of the rock can damage their tissue.
In contrast, lawn algae grow on the outside of 1.
Square plastic bottle (
Fiji Water Company, California, United States of America)
In 1 metre of chicken-wired cages (
Net lawn algae 0. 20u2009±u20090. 01; 5. 78u2009±u20090. 37; spp. 0. 46u2009±u20090. 06; 0. 39u2009±u20090. 01; spp. 0. 24u2009±u20090. 02; 0. 34u2009±u20090. 01; spp. 0. 48u2009±u20090. 05; 0. 31u2009±u20090. 02.
Because it is a calcium algae, its dry weight is higher than that of other marine algae.
Ideally, we would mimic the nutrient concentrations we found in the Coral Reef sediment plume ().
However, when we started our lab experiments, we did not yet have nutritional data from the sediment plume.
So we chose the following five nutritional treatments (end-concentrations)
Based on the early experiment of coral reef nutrition :(1)low NH (5u2009μM)and (2)high NH (50u2009μM)
NHCl is added to the filtered natural seawater for treatment; (3)high NO (25u2009μM)
Adding nano-treatment; (4)low PO (0. 88u2009μM)and (5)high PO (1. 75u2009μM)
Treatment by adding KHPO.
These nutrient concentrations reflect at least a natural increase in nutrient concentrations during the runoff event (e. g.
, Lapointe and Costa with references).
Every nutritional treatment, a nutrition database (i. e.
One of the above five nutritional treatments)
It\'s in a different 25-
On the same day, the nutrient absorption experiment of a liter of plastic containers was carried out.
We used ten glass jars to process each plant and each nutrient.
Each time we performed a nutrient absorption experiment, we used only one species from 5 or 20 µm depth and only one of the five nutrient treatments was applied (i. e.
We do nutrient absorption experiments once a day).
The species we are going to investigate are placed in 9 of the 10 glass jars (
N = rw9 for each nutritional treatment)
, The tenth tank is used as a control to ensure that the nutrient concentration remains the same in the absence of undersea organisms.
For experiments involving lawn algae, a clean plastic strip was added to the control Glass to check whether the plastic that the lawn algae breed affects the nutrient concentration in the jar.
Since the nutrient concentration remained unchanged in all controls, the observed nutrient concentration changes during the experiment were attributed to the organism placed in the jar.
Ten glass jars are placed in a large aquarium. 80x40x20 cm).
The water level at the aquarium is too low to enter the jar, but the circulating fresh seawater ensures that all the samples have gone through temperatures similar to that of the coral reef (27–29u2009°C).
Use Vibra for each jar-inflate separately
Aquarium 2 or 3 Aquarium Air Pump (
Blue Ribbon pet products, New York, USA)
Equipped with 0.
22 μm top plate filter to minimize potential air pollution.
Throughout the absorption experiment, the gentle bubbling of the water ensures constant movement of the water in the jar.
The 10 50-watt spotlights provide a constant light intensity of 200 μ mol photon m s using LI-
Data logger 1000 (LI-
Lincoln, Lincoln, United States of America)
, Which is similar to the light conditions measured at our study site at a depth of 20 m on a sunny day.
This light availability is sufficient (almost)
Saturated light conditions for all species in our study, except according to photosynthesis
Radius curve (nu2009=u20095)made .
Therefore, the ten light spots used in laboratory nutrient absorption experiments should provide sufficient light for most organisms collected at 5 and 20 metres in depth.
Coral is an exception because its photosynthesis rate still increases almost linearly with the irradiance of 200 μ mol photon m s and at a high irradiance above 800 mu mol μ mol photon m s.
The uptake rates of NH and PO were determined by the reduction of NH and PO concentrations in each jar over time. This so-
Called \"retracement method\" is a simple and effective method.
Methods for Large algae, corals and even algae have been established, with the advantage that the absorption rate can be quickly determined at different external nutrient concentrations.
The first water sample was taken before putting the organism into the jar.
After adding the organism, 5 ml of water samples were collected at a specific time interval.
In NH absorption experiments, water samples were collected after 10, 20, 30, 60 and 120 min.
In the PO intake experiment, water samples were taken after 10, 20, 30, 40, 50 and 60 min, and the detection limit of PO was often reached at this time.
Water samples were collected in NH or PO absorption experiments and filtered through 0 immediately.
22 μm sterile top plate filter (
Pall, New York, USA)
Packed in 6ml polyethylene vials (
MA, PerkinElmer, United States of America).
According to The hommes and Murphy & Riley, the NH and PO in water samples were analyzed immediately using the T60 visual spectrometer (
Wibtoft PG instruments, UK).
At the end of the culture experiment, quickly rinse algae and blue bacteria with distilled water and store them in pre-
Weighing aluminum foil at-20 °c
The sample was frozen.
Dry overnight in Scanvac CoolSafe freezedryer (
Science B. Scala. V.
Yide, Netherlands)
Determine their dry weight.
According to Hardt, the total dry weight of all living tissues is approximate from its surface area.
Maximum NH and PO uptake rate (V)
The total intake per species is based on the first 10 minutes (i. e. , tu2009−u2009t)
And expressed in Mu mol g DW h.
V is calculated only from nutrient absorption experiments using high initial nutrient treatment (i. e. , 50 μm NH or 1. 75u2009μM PO)
V of all species studied due to the highest initial nutrient concentration persistence.
At kurasau island, we did not have the opportunity to measure the absorption of NO By luminosity, as we lacked cadmium, titanium chloride and ammonia in the required NO reduction analysis.
Therefore, the NO absorption rate was determined by adding stable isotope N to the 2 u2009 h incubation period.
At the beginning of each incubation, 25 μm NaNO (
98 at %, Sigma Aldrich, Zwijndrecht, Netherlands)
Was added to nine glass tanks containing undersea organisms, while the tenth glass tank was used as a control by hatching the corresponding organisms without adding Nano.
The N concentration of control organisms is used as a reference for the N concentration of biological background (i. e.
, Control sample).
After hatching for 2 hours, the dry weight of coral, algae and blue bacteria was similar to the estimate During NH and PO absorption experiments (see above).
The tissue ΔN content of the sample was determined by thermal finnigan Δplus isotope ratio mass spectrometry (Bremen, Germany)
Flash 1112 element analyzer connected to Carlo Erba instrument (Milan, Italy).
Grind algae samples into powder and transfer them to tin capsules (
Size: 12x6x6mm)
Folded into small balls.
NO can be absorbed by corals, but not by animals.
To analyze the uptake rate of NO in coral by Coral worms, coral tissue was removed from the underlying skeleton using a toothbrush and suspended in a 15 ml tube containing filtered seawater (Whatman GF/F).
Centrifuge twice in the EBA 21 centrifuge at 4000rpm for 20 minutes (
Bch, hetich laboratory, Germany)
Concentrate Cordyceps on the bottom of the test tube.
Move liquid from the tube and filter to the pre-filtered Whatman GF/F filter
Use the air recycling chamber furnace to burn for 4 hours at 450 °c (
Sulphur plastic, Linggu, United Kingdom)
And save at least 3 days-20 °c before freezingdried.
Because, the Whatman GF/F filter loaded with worm grass worm is packed directly into tin capsules and folded into small particles. The powder (
Algae and blue bacteria)or filter (zooxanthellae)
Weighing in tin capsules, its ΔN content (in ‰)
Quantified as: where is the isotope ratio N/N of the sample, the isotope ratio of atmospheric N (i. e. , u2009=u20090. 0036765).
Calibration of ΔN measurements according to laboratory standard urea (δNu2009=u2009−40. 81‰)
And ketone (δNu2009=u20091. 3‰).
No uptake rate (
DW h in Mu mol N g)
The nitrogen content of each species is calculated as follows: where is the nitrogen content of the tissue (in mmol N g DW)
, Is the incubation time of 2 hours, ΔN is ΔN of N-
Enriched samples, ΔN is the ΔN of the control sample, which is the atomic concentration (at%)
We provide N in the nitrate pulse.
Calculate the V of NO by dividing the V in equation 2 by two hours and represent it in μ mol g DW h
NH and PO uptake rate (V)
As a function of the nutrient concentration in the medium.
Since the nutrient concentration changed during the absorption experiment, we chose to use three continuous time points to calculate the moving average of the nutrient concentration to suppress the measured noise in the nutrient data (e. g.
The nutrient concentration at T is calculated ([t]+u2009[t]+u2009[t]/3).
If the absorption pattern of an organism is two-way, the initial nutrient absorption rate (surge uptake)
The first 10 minutes of the experiment were excluded from this analysis.
In addition, the negative nutrient absorption rate (
Obtained when nutrient concentrations are occasionally increased in absorption experiments)
It was also excluded from the analysis.
Calculated speciesand nutrient-
Specific absorption rates are used to estimate how different members of the coral reef community use the nutrition delivered by the curtain-type nutrient pulse.
The absorption of nutrients by coral reef communities composed of species can be described by the following differential equations: where is the nutrient concentration in the nutrient plume, the total amount of nutrients in the species ,()is the biomass-
The specific nutrient absorption rate of the species is a function of the environmental nutrient concentration, the biomass of the species, and the rate at which the nutrient concentration in the plume is reduced through other processes (e. g.
, Mixed with open seawater, anti-nitrogen).
Because it is not feasible to measure the nutrient absorption dynamics of all species, we assume that the nutrient absorption rates of all hard corals at our study site are representative.
Similarly, we assume the average uptake rate of the spp.
And represent the uptake rate of blue bacterial pads at 5 m depth at our research site, and represent the uptake rate of blue bacterial pads at 20 m depth (i. e. , spp.
Did not happen at the depth of 5 CUCM at our research site).
If the nutrient absorption rate of the species is linearly dependent on the environmental nutrient concentration (i. e. , ()=u2009)
Differential Equations (3)
It can be solved by reducing the nutrient concentration in the time environment: where is the initial nutrient concentration in the nutrient plume.
Each species that obtains nutrients is a further equation (5)into equation (4)
And subsequent integration, which leads to: where is the initial amount of nutrients in the tissue of the species. Equation (6)
Show a small percentage per species /(Σu2009+u2009)
Nutrients transmitted by pulse.
Therefore, species with more biomass and/or higher nutrient absorption rates will get a larger share of total nutrient input.
For our research site, the size of the parameters is unknown.
Therefore, we cannot accurately estimate which part of the nutrient in the sediment plume disappears into the open ocean or is absorbed by plankton.
However, from the measured nutrient absorption rate and biomass of the species studied, we can calculate the fraction/σ, indicating the proportion of nutrients absorbed by different members of the coral reef community at our research site. Two-
Sample of studentstests (
Equal variance)or Welch’s -tests (
For unequal variance)
Used to test whether the nutrient concentration in normal seawater after heavy rainfall is different from that in sediment plume.
We applied for two.
Test the maximum nutrient absorption rate (V)
Different species and different depth
Origin of Species (i. e.
, To study the effect of depth on V, we only include creatures found in depth of 5 and 20 m on reefs).
Data is log-
If this improves the uniformity of the variance, it is converted, as tested by Levene\'s test. Post-
The special comparison of these means is based on the HSD test of Tukey using the significance level (α)of 0. 05.
The nutrient absorption rate can follow a two-way pattern, that is, the highest nutrient absorption after the nutrient pulse, but then transfer to a lower absorption rate.
We tested the presence of this bipolar pattern by determining the nutritional uptake rate of the first 10 minutes of the experiment (Time interval t)
Significantly higher than the uptake rate in the next 10 minutes (Time interval t)
Using paired samplestests.
Linear regression was used to test whether the nutrient absorption rate increased significantly as the ambient nutrient concentration increased.
Using Shapiro-to evaluate normality and variance of residual values in regression analysisWilk test (αu2009=u20090. 05)
Through visual inspection of the residue respectively. The Shapiro-
The Wilk test shows that the distribution of residual values conforms to the normal assumption in almost all cases.
The only exception is the PO uptake rate, and all data points are near the regression line except one ().
The normal test passed when this data point was deleted, but we decided to keep this data point because linear regression is often very robust for deviations from normal, and there is no clear reason to delete this particular point as an exception point.
Visual inspection showed that most residual values were consistent with the consensus assumption of linear regression, but with the increase in NH concentration, and the increase in the size of lawn algae residual values ().
However, we did not change the rate of absorption of NH with lawn algae to increase the homogeneity, because other regressions in and do not show signs of variance, we prefer to apply the same statistical analysis to all species.
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