Phytoplankton Types Research Articles

High Spatiotemporal Dynamics of Methane Production and Emission in Oxic Surface Water.

The discovery of methane (CH4) accumulation in oxic marine and limnic waters has redefined the role of aquatic environments in the regional CH4 cycle. Although CH4 accumulation in oxic surface waters became apparent in recent years, the sources are still subject to controversial discussions. We present high-resolution in situ measurements of CH4 concentration and its stable isotope composition in a stratified mesotrophic lake. We show that CH4 accumulation in surface waters originates from a highly dynamic interplay between (oxic) CH4 production and emission to the atmosphere. Laboratory incubations of different phytoplankton types and application of stable isotope techniques provide a first unambiguous evidence that major phytoplankton classes in Lake Stechlin per se produce CH4 under oxic conditions. Combined field and lab results show that the photoautotroph community is an important driver for CH4 production and its highly dynamic accumulation in oxic surface waters.

An Empirical Algorithm using Derivative Difference for Estimating Chlorophyll-A in Case-II Water

Water quality management includes measurement of quantity and quality. The abundance of phytoplankton in water body represents the physical condition and chemical constituents. As Chlorophyll-a exists in all types of phytoplankton, naturally the choice for water quality measurement is estimation of Chl-a concentration. The Chl-a concentration is estimated using various spectral reflectance algorithms such as single band regression, band ratio, three-band ratio, four-band ratio etc have been developed and is being used. Subsequently, the first order derivative ratio and second order derivative ratio methods are also used in some studies. Though such algorithms provide water quality measures, new algorithms are being introduced to improve estimation accuracy. In this paper, a new algorithm ‘Derivative Difference’ is proposed. It is based on the Chlorophyll concentration variation with shape of reflectance spectrum. The derivative data represents the slope of the reflectance data at different wavelength. The difference in derivative values at selected two different wavelengths were correlated with measured values to estimate Chl-a concentration. Obtained results were compared with the values obtained from band ratio method and derivative ratio methods. The algorithm is found to be better in some conditions.

Partitioning of iron and plutonium to exopolymeric substances and intracellular biopolymers: A comparison study between the coccolithophore Emiliania huxleyi and the diatom Skeletonema costatum

Iron (Fe), a micronutrient for algal growth, and plutonium (Pu), an anthropogenic radionuclide, share some common features. This includes similar oceanic distributions when different input modes are taken into account, as well as their chemical behavior, such as a high affinity to natural organic matter (NOM). The NOM produced by various phytoplankton communities can potentially influence Fe cycling in the ocean, and likely also influence the transport behavior of Pu. We conducted laboratory incubation experiments using the coccolithophore Emiliania huxleyi and the diatom Skeletonema costatum, in the presence of 59Fe and 238Pu as radiotracers, in order to differentiate Fe and Pu uptake by extracellular exopolymeric substances (EPS) and intracellular biopolymers. The Fe and Pu distributions in select organic compound classes produced by these two types of phytoplankton, including proteins, total carbohydrates (TCHO) and uronic acids (URA), were compared. Our results indicated that most of the Fe and Pu (>95%) were found concentrated in E. huxleyi-derived non-attached EPS, while much less (<2%) was present in the intracellular fraction of E. huxleyi. In contrast, in the diatom S. costatum, Fe and Pu were both distributed with EPS > intracellular biopolymers > outer cell covering (i.e., frustule). In fact, over 50% of the Fe was concentrated in S. costatum-derived attached EPS and intracellular biopolymers. The diatom derived Fe-EPS complexes were more hydrophobic, with stronger tendency to aggregate in seawater. Fe binding to biopolymers in both E. huxleyi and S. costatum cultures was related to URA concentrations, but the overall distribution of URA between these two phytoplankton species was different (e.g., high intracellular abundance of URA in S. costatum but low intracellular URA abundance in E. huxleyi). Our findings suggest that the presence of URA on cellular surfaces of S. costatum (i.e., attached EPS) and its high intracellular fraction could be an indicator for Fe transport from the surrounding seawater to the diatom cells. However, for the coccolithophore E. huxleyi, Fe was not efficiently taken up during its growth. Instead, the more hydrophilic non-attached EPS (i.e., low protein/TCHO ratio) produced by E. huxleyi could have stabilized Fe in the colloidal form as Fe-EPS complexes. Similar partitioning behavior of Fe and Pu suggests that Pu isotopes can potentially serve as a tracer for Fe biogeochemistry in the ocean.

Global ocean primary production trends in the modern ocean color satellite record (1998–2015)

Ocean primary production (PP), representing the uptake of inorganic carbon through photosynthesis, supports marine life and affects carbon exchange with the atmosphere. It is difficult to ascertain its magnitude, variability, and trends due to our inability to measure it directly at large scales. Yet it is paramount for understanding changes in marine health, fisheries, and the global carbon cycle. Using assimilation of ocean color satellite data into an ocean biogeochemical model, we estimate that global net ocean PP has experienced a small but significant decline −0.8 PgC y−1 (−2.1%) decade−1 (P < 0.05) in the 18-year satellite record from 1998 to 2015. This decline is associated with shallowing surface mixed layer depth (−2.4% decade−1) and decreasing nitrate concentrations (−3.2% decade−1). Relative contributions to PP by various types of ocean phytoplankton have changed, with decreases in production by intermediate-sized phytoplankton represented by chlorophytes (−14.3% decade−1). This is partially compensated by increases from the unique, more nutrient-efficient, coccolithophores (8.4% decade−1). Geographically, the North and Equatorial Indian Oceans are responsible for much of the decline in PP, falling 0.16 and 0.69 PgC y−1 decade−1, respectively. Reduced production by large, fast-growing diatoms along with chlorophytes characterizes the decline here. In contrast, increases in PP are found in the North and North Central Pacific. The increases here are led by chlorophytes in the North Pacific and the small cyanobacteria in the North Central Pacific. These results suggest that the multi-decadal satellite observational record, coupled with an underlying representation of marine biodiversity in a model, can monitor the uptake of carbon by phytoplankton and that changes, although small, are occurring in the global oceans.

JENIS FITOPLANKTON DI SUNGAI PANJARATAN SEBAGAI BAHAN AJAR KONSEP PROTISTA SMA KELAS X

Learning is currently using the scientific approach, through direct interaction with lea rning resources. The educator or teacher at the school are expected to use appropriate learning resources. Local potentials that are spread around in the form of learning resources should be of concern to organized, so empowering positive for all students' learning. Not much research to develop teaching materials based on local potential. The amount of biological material that can not be observed directly, such as materials about protists, monera, one-celled animals, make the learners have difficulty to understanding. Research types of phytoplankton can be used as a learning resource to overcome these problems. This research aims to (1) Produce teaching materials of research types of phytoplankton in Panjaratan River (2) Examine the feasibility of teaching materials that are based on research on the type Phytoplankton Panjaratan River. The results showed (1) teaching materials produced are teaching materials enrichment entitled Type Phytoplankton in the River Panjaratan, consisting of 3 BAB, teaching materials prepared in accordance competencies and according to the terms of teaching materials quality that meets aspects of the display, the aspect of the presentation of the material and aspects of language , (2) Eligibility teaching materials in the river Panjaratan Phytoplankton type of expert validation result is quite valid with an average score of 80,43%, readability test students strongly agree with the assessment statement as much as 53,1%, 45,03% agree and 1,87% disagree . Assessment of teachers partners on quite valid with an average score of 76,12%. Results responses of teachers and students each showed a good response. Learning outcomes after using teaching materials in the river Phytoplankton type Panjaratan increase seen from the posttest and normality test Gain (n-gain) with an average value of 83,7 and a gain of 0,81 postest with high improvement category.

IDENTIFICATION OF PHYTOPLANKTON TYPES IN TAMBAK BANDENG WITH HIGH QUALITY OF OMEGA-3

Microalgae as a source of nutrients, can be a good alternative to the use of high-level organisms. The abundant omega 3 content in plankton, especially phytoplankton, needs to be conducted research on the identification of the types of phytoplankton in milkfish with high omega-3 quality. The purpose of the study was to identify the types of plankton containing omega-3 and to determine the levels of omega-3 from plankton found in milkfish ponds. This research was conducted at the Laboratory of the Faculty of Fisheries and Marine Sciences, Brawijaya University, Malang. The highest abundance of phytoplankton is from the Bachillariophyta division and the lowest division euglenophyta. Five types of plankton were determined to be tested for omega-3 fatty acids using the gas chromatography (GCMS) method, namely: Chaetoceros sp, Tetraselmis sp, Nitzchia, Chlorella and Spirulina. GCMS test results from several types of omega-3 fatty acid plankton isolates in Chaetoceros calcitrans were the highest compared to the other 4 plankton types. Conclusion of the composition of plankton in traditional pond waters consists of 4 phytoplankton divisions namely Chlorophyta, Chrysophyta, Cyanophyta, and Euglenophyta. GCMS test results from several types of plankton isolates omega-3 fatty acids in Chaetoceros sp, the highest compared to Tetraselmis sp, Nitzchia , Chlorella and Spirulina. Suggestion of natural feed in the water of milkfish ponds should use Chaetoceros sp because the content of omega 3 is high. Keywords: phytoplankton, omega-3

ANALYSIS OF CAUSING FACTORS ON THE APPEARANCE OF HABS IN COASTAL WATER OF MAKASSAR

HABs were types of phytoplankton considered dangerous in the sea. Its appearance was triggered by an increase in nutrients and the presence of physical and chemical factors in the optimal conditions to support its growth. For that reason, research on the analysis of the causes of the emergence of HABs in the coastal waters of Makassar has been carried out. The implementation is carried out from March to June 2017 using non-experimental methods. The results showed that there were seven types of HABs, such as Protoperidinium, Gymnodinium, Ceratium, Prorocentrum, Gyrodinium, Gonyaulax, and Dinophysis. That types from the Dinophyceae Class. The appearance of the types of HABs was due to the influence of temperature with the relationship were very strong and positive.

Distribution of phytoplankton diversity and abundance in Maspari island waters, South Sumatera, Indonesia

Phytoplankton diversity is one of eutrophication indicator in Maspari island, south Sumatra, but its existence is strongly influenced by the physical-chemical parameters of the waters. This study aims to determine the distribution of phytoplankton diversity and their relationship with physical-chemical parameters in the waters of Maspari island. The methodology of research carried out was the physical-chemical parameter data collection, and phytoplankton samples were taken randomly on the surface of the water of 20 stations. Samples were identified types, analysed diversity, dominance and abundance calculations. For the relationship between diversity and abundance of phytoplankton with physical-chemical parameters of water carried out by principal component analysis (PCA). The results obtained that some of the physical-chemical parameters of Maspari Island waters have high variations such as turbidity ranging from 17,313 to 89,313 FTU. Current speed about 0.0-1,418 m.s−1. Dissolved oxygen about 3.78±0.18-6.18±0.15 mg.1−1. Nutrient concentrations such as NO3 about 0-0.28 mg.l−1 and PO4 about 0-0.2 mg.1−1, while the other parameters were smaller variations. Phytoplankton types found in four classes, namely Coscinodiscophyceae (7 species) with an abundance of 121,910.82 cell.m−3 (49%), Dinophyceae (4 species) with an abundance of 54,649.68 cell.m−3 (26%), Bacillariophyceae (3 species) with an abundance of 56,050.95 cell.m−3 (23%), and Fragilariophyceae (1 species) with an abundance of 5,605.09 cell.m−3 (2%). Diversity index shows low to moderate categories, while dominance in categories tends to dominate. PCA results showed that the physical-chemical parameters of the Maspari island waters of the identifier is the temperature, density, nitrate, salinity, DO and phosphate.

Co-occurrence patterns between phytoplankton and bacterioplankton across the pelagic zone of Lake Baikal during spring.

Phytoplankton and bacterioplankton play a key role in carbon cycling of aquatic ecosystems. In this study, we found that co-occurrence patterns between different types of phytoplankton, bacterioplankton, and environmental parameters in Lake Baikal during spring were different over the course of three consecutive years. The composition of phytoplankton and bacterial communities was investigated using microscopy and 16S rRNA gene pyrosequencing, respectively. Non-metric multidimensional scaling (NMDS) revealed a relationship between the structure of phytoplankton and bacterial communities and temperature, location, and sampling year. Associations of bacteria with diatoms, green microalgae, chrysophyte, and cryptophyte were identified using microscopy. Cluster analysis revealed similar correlation patterns between phytoplankton abundance, number of attached bacteria, ratio of bacteria per phytoplankton cell and environmental parameters. Positive and negative correlations between different species of phytoplankton, heterotrophic bacteria and environmental parameters may indicate mutualistic or competitive relationships between microorganisms and their preferences to the environment.

Monitoring water quality in Singapore reservoirs with hyperspectral remote sensing technology

Abstract In this work, algorithms were developed for retrieving water quality parameters related to Singapore's reservoirs. The main constituents that affect the water reflectance (WR) – i.e. proportion of incident light reflected from the surface of water bodies after removing the surface glint component – are the suspended particles, phytoplankton and coloured dissolved organic matter (CDOM). The existing absorption spectrum model for phytoplankton in seawater is not accurate for the phytoplankton types that exist in the fresh water environment. The phytoplankton absorption spectrum was modelled by a series of Gaussian peaks from 400 to 750 nm. The peak strengths were dynamically derived from the WR measured. The phytoplankton absorption model is incorporated into a semi-empirical WR model for retrieving the absorption and backscattering coefficients of water components such as suspended sediments, CDOM and phytoplankton. The chlorophyll-a concentration and water turbidity estimated using this model correlate well with field sampling measurements, with coefficients of determination (R2) exceeding 0.8.

Periphython Epilithic Community Structure in Cikamal Estuary and Cirengganis Estuary, Pananjung Pangandaran, West Java

Nailah S, Rosada KK. 2018. Periphython Epilithic Community Structure in Cikamal Estuary and Cirengganis Estuary,Pananjung Pangandaran, West Java. Pros Sem Nas Masy Biodiv Indon 4: 236-241. Periphyton is one of the biotic communities that canlive well in the waters. Epilithic periphyton is cosmopolitan and allows standardization for spatial or temporal comparisons, therefore itis often used to determine the quality status of a water. The purpose of this research is to know the structure of epilithic periphytoncommunity in Estuary of Cikamal River and Estuary of Cirengganis River Pananjung Pangandaran. The method used is exploration. Ineach study site, samples of periphyton and water were taken. At the time of sampling, physicochemical parameters measured weretemperature, brightness, depth, light intensity, salinity, current velocity, pH, and DO. The results showed that the periphyton in bothestuaries consisted of phytoplankton, zooplankton, and microbenthos. In general, the abundance of phytoplankton is higher compared tothe other two groups. Periphyton in Estuary of Cikamal River found 19 species of phytoplankton, one type of zooplankton, and one typeof microbenthos, while in Estuary of Cirengganis River found 24 types of phytoplankton, nine types of zooplankton, and three types ofmicrobenthos. Periphyton density at Estuary of Cirengganis River is higher than periphyton at Estuary of Cikamal River. The higherdiversity of periphyton species is found in Estuary of Cirengganis River. The periphyton at the Estuary of Cirengganis River has ahigher evenness than the periphyton at the Estuary of Cikamal River. One species that dominates on both estuaries is Navicula sp. Basedon the Sorensen similarity index, both estuaries have a moderate level of community similarity. The water quality of Estuary of CikamalRiver is included into the heavily polluted waters whereas the Estuary of Cirengganis River belongs to the medium contaminated waters.

Unraveling Phytoplankton Community Dynamics in the Northern Chukchi Sea Under Sea‐Ice‐Covered and Sea‐Ice‐Free Conditions

AbstractThe timing of sea ice retreat, light availability, and sea surface stratification largely control the phytoplankton community composition in the Chukchi Sea. This region is experiencing a significant warming trend, an overall decrease in sea ice cover, and a documented decline in annual sea ice persistence and thickness over the past several decades. The consequences of earlier seasonal sea ice retreat and a longer sea‐ice‐free season on phytoplankton community composition warrant investigation. We applied multivariate statistical techniques to elucidate the mechanisms that relate environmental variables to phytoplankton community composition in the Chukchi Sea using data collected during a single field campaign in the summer of 2011. Three phytoplankton groups emerged that were correlated with sea ice, sea surface temperature, nutrients, salinity, and light. Longer ice‐free duration in a future Chukchi Sea will result in warmer sea surface temperatures and nutrient depletion, which we conclude will favor other phytoplankton types over larger diatoms.

Effect of water irrigation volume on Capsicum frutescens growth and plankton abundance in aquaponics system

This study aimed to understand Capsicum frutescens growth and plankton abundance in aquaponics culture. A Completely Randomized Design (CRD) with six treatments in triplicates comprising of treatment A (positive control using organic liquid fertilizer), B (negative control without fertilizer), C (drip irrigation aquaponics with a water debit of 100 ml/day/plant), D (drip irrigation aquaponics with a water debit of 150 ml/day/plant), E (drip irrigation with a water debit of 200 ml/day/plant), and F (drip irrigation aquaponics with a water debit of 250 ml/day/plant) was applied. The water used in treatments C, D, E, and F contained comet fish feces as fertilizer. C. frutescens growth and plankton abundance were observed. Analysis was conducted using analysis of variance for plant productivity and descriptive analysis for plankton abundance and water quality. The results of this study showed that the highest plant growth was seen in plants receiving F treatment with 50 ml/day drip irrigation. However, no significant difference was found when compared to the positive control with organic artificial fertilizer. Eleven types of phytoplankton and six types of zooplankton were found, with Stanieria sp. as the most abundant phytoplankton and Brachionus sp. and Epistylis sp. as the most abundant zooplanktons.

Spring phytoplankton community response to an episodic windstorm event in oligotrophic waters offshore from the Ulleungdo and Dokdo islands, Korea

We investigated the phytoplankton distribution and its relationship to environmental factors at 40 stations in oligotrophic waters offshore from the Ulleungdo and Dokdo islands (hereafter Ulleungdo or Dokdo) in Japan/East Sea, prior to and following an episodic windstorm event. Nutrient addition bioassay experiments (control, +N, +P, and +NP, in both the presence and absence of added Fe) were also conducted to investigate the growth response of the phytoplankton assemblage and its nutrient consumption, using surface seawater collected from stations 36 and 40, which are in the vicinity of the Dokdo. Field measurements showed that the surface water temperature ranged from 13.33°C to 16.18°C and the salinity ranged from 34.03 to 34.55. The nitrate+nitrite, phosphate, and silicate concentrations varied from 0.07 to 2.22μM, 0.01μM to 0.19μM and 0.76 to 6.93μM, respectively. The Chl-a concentration varied from 0.36 to 15.97μgL−1 (average 2.66±3.26μM), but was significantly higher in Zone III-a (Dokdo) than in Zone I-b (between Ulljin and Ulleungdo, prior to the windstorm), Zone I-a (between Ulljin and Ulleungdo, following the windstorm), and Zone II-a (Ulleungdo) (F=17.438, p<0.001; ANOVA). Diatoms and Raphidophyta were the dominant phytoplankton types. Following episodic windstorm events the abundance of the raphidophyte Heterosigma akashiwo was maintained at high levels in the offshore oligotrophic area around the Ulleungdo and Dokdo, particularly in Zone III-a (F=16.889, p<0.001; ANOVA). In the algal bioassays conducted with and without added Fe, the in vivo fluorescence values in the +N and +NP treatments were higher than in the control and the +P treatments, which suggests that plankton biomass production was stimulated by N availability. In the +N and +NP treatments, H. akashiwo typically dominated in the initial, logarithmic, and stationary growth phases. The growth rate of the phytoplankton community in the presence of added Fe was not statistically different (p>0.05) from that in the treatments without added Fe. The results suggest that in this area natural phytoplankton communities, including those dominated by H. akashiwo, respond rapidly to pulsed nitrogen loading events. The episodic windstorm event probably resulted in vertical mixing that brought nutrients into the euphotic upper layer. The results suggest that such events are important in triggering spring phytoplankton blooms in potentially oligotrophic waters, such as those in the vicinity of the Dokdo in the Japan/East Sea.

Variability of chlorophyll-a and diatoms in the frontal ecosystem of Indian Ocean sector of the Southern Ocean

Abstract Phytoplankton composition plays a major role in biogeochemical cycles of the ocean. The intensity of carbon fixation and export is strongly dependent on the phytoplankton community. Yet, the contribution of different types of phytoplankton to the total production on various communities is still poorly understood in the Indian Ocean sector of Southern Ocean (SO). Therefore the variability of chlorophyll-a (Chl-a) and diatoms in the frontal ecosystems of the Indian sector of SO have been investigated along with the sea surface temperature (SST), sea surface wind (SSW), photosynthetically active radiation (PAR), and nutrients datasets for the period of 1998–2012. Combined analysis of in-situ, model and satellite observations indicate that the variability of Chl-a and diatoms were primarily influenced by light and wind. The Chl-a was higher at the sub-Antarctic front (SAF) followed by the sub-tropical front (STF) and the polar front (PF). The diatom concentration was higher at the SAF followed by the PF and STF. Maximum concentration of Chl-a and diatoms commonly observed at the SAF region are probably due to the moderate PAR, SST and wind. Dominance of diatoms at the PF may be attributed to their adaptability for low light conditions. The results from this study in the frontal ecosystems would help to understand the biogeochemical cycle of the Indian sector of the SO.

Control effect of periodic variation on the growth of harmful algal bloom causative species

Blue-green algae and Dinoflagellate etc. are common types of phytoplankton as causative species which cause the harmful algal blooms (HABs). The growth process of causative species is complex according to the variation of the environmental disturbance such as the periodic factor in reality and recent studies have not revealed the secret of the growth complexity yet. Based on the empirical and theoretical results of the growth of causative species, a nonlinear controlled system with periodic factor was obtained and the different effects of the periodic factor on the control of the cell density and the growth rate of causative species were studied by three theorems using the norm theory and finite difference method. Simulations and experimental data were also used to assess the effectiveness of the controlled results.

PENGARUH INTENSITAS MUSIM HUJAN TERHADAP KELIMPAHAN FITOPLANKTON DI WADUK BENING SARADAN

This study aims to determine the effect of the intensity of the rainy season to the abundance of phytoplankton in the reservoir Bening Madison County. As well as exploit some results of research on the abundance of phytoplankton as a medium of learning materials were shaped poster on the types of phytoplankton. This study uses a quantitative approach to the exploration technique. There are six points each station with two sample replicates. The results showed that in Reservoir Bening Saradan found 16 species of phytoplankton that is Synedra acus, Synedra ulna, Navicula grevillei, Tetragonodium verum, Crucigenia rectangularis, Ulothrix cylindricum, Nitzchia paleaceae, Ceratium candelabrum, Goniochloris sculpta, Scenedesmus ocuminatus, Navicula sp, Nitzchia acicularis, Spirulina major, Ceratoneis acus, Pediastrum simplex, Pleurota eniumtrabecula. Phytoplankton abundance is the most ubiquitous class Bacillariophyceae. Phytoplankton abundance is influenced by monsoon intensity 40,9%. While 59,1% of other factors influenced the agricultural wastes that contain elements of N, P, K, which can improve nutrient. The highest phytoplankton abundance in December is 138,64 ind/l with 12 species of phytoplankton. The number of rainy days in the December low at 25/31 days allows a maximum of phytoplankton photosynthesis. Lowest phytoplankton abundance in February which is 65,14 ind/l. Phytoplankton abundance is directly proportional to the intensity of the rainy season. The number of higher intensity, phytoplankton abundance is also higher, and vice versa. Physical and chemical conditions Bening Reservoir categorized according to the results of research in the waters of the state are less fertile and less than optimal for the growth ofphytoplankton.

Competition and community assemblage dynamics within a phytoplankton functional group: Simulation using an eddy-resolving model to disentangle deterministic and random effects

To advance our understanding of competition and coexistence in phytoplankton species within a functional group, such as a diatom group, we developed a numerical model composed of 240 within-tropic-level virtual species that can actually or potentially compete. We then explored how the phytoplankton assembly is structured by deterministic or stochastic processes, where the former process is typically represented using the traditional niche theory and the latter process is highlighted using the neutral theory. Because we used eddy-resolving resolution, phytoplankton dispersion and the resultant dispersal limitation were explicitly represented, where the dispersal limitation prevents the most competitive species from using its appropriate niche and subsequently enhances stochastic effects. In the simulation results, all surviving species have an oceanic volume in which the phytoplankton species has the highest specific growth rate in all the 240 species. The abundance in the most competitive space has a strong positive correlation with the relative species abundance. Moreover, of the phytoplankton types whose abundances in the most competitive space are nearly equal, the survival of a species is affected by its residence time within its habitat; the surviving phytoplankton species tend to have larger residence times compared to the non-persistent species. These results led us to conclude that deterministic processes had significant contributions to a formation of phytoplankton assembly. This was supported by the result that a structure of phytoplankton assembly represented by species rank in abundance was invariant with time and hardly dependent on initial conditions of phytoplankton composition.

Comparison of Phytoplankton Communities in Catfish Split‐Pond Aquaculture Systems with Conventional Ponds

AbstractThere has been a growing interest and use of variations of partitioned aquaculture systems (PAS) in recent years by the southeastern U.S. catfish farming industry. Split‐pond systems, one type of PAS, are designed to better manage fish waste byproducts (e.g., ammonia) and dissolved oxygen levels than the conventional earthen ponds that have been used by farmers for many decades. Recent studies have focused on design, water flow rates, and other management areas of catfish split‐ponds, but so far there has not been a focused examination of phytoplankton community composition and biomass in these split‐ponds. In the current study, pond water samples were collected from split‐ponds at a research facility in western Mississippi and at a commercial fish farm in western Alabama approximately every 3 weeks during the fish grow‐out period (May to November). Water samples were analyzed for chlorophyll a concentration (phytoplankton biomass) of several major phytoplankton divisions and for types of phytoplankton and their abundance. Overall, chlorophyll a concentrations in the split‐ponds were maintained within the typical range (0–800 µg/L) found in non‐PAS (conventional) catfish ponds. The phytoplankton communities in split‐ponds were dominated by cyanobacteria or blue‐green algae (Cyanophyta) and by the same common species of cyanobacteria (e.g., Planktothrix agardhii, P. perornata, Microcystis aeruginosa, Raphidiopsis brookii) reported in previous studies for conventional catfish ponds. In addition, many types of phytoplankton in the other major divisions—Chlorophyta (green algae), Bacillariophyta (diatoms), Chrysophyta (golden brown algae), Cryptophyta (cryptomonads), Euglenophyta (euglenophytes), and Pyrrhophyta (dinoflagellates)—present in the split‐ponds were the same as those reported previously in conventional catfish ponds. Therefore, issues related to management practices for pond water quality (e.g., dissolved oxygen) and undesirable cyanobacteria are expected to be similar to those used for conventional ponds.

Role of zooplankton dynamics for Southern Ocean phytoplankton biomass and global biogeochemical cycles

Abstract. Global ocean biogeochemistry models currently employed in climate change projections use highly simplified representations of pelagic food webs. These food webs do not necessarily include critical pathways by which ecosystems interact with ocean biogeochemistry and climate. Here we present a global biogeochemical model which incorporates ecosystem dynamics based on the representation of ten plankton functional types (PFTs): six types of phytoplankton, three types of zooplankton, and heterotrophic procaryotes. We improved the representation of zooplankton dynamics in our model through (a) the explicit inclusion of large, slow-growing macrozooplankton (e.g. krill), and (b) the introduction of trophic cascades among the three zooplankton types. We use the model to quantitatively assess the relative roles of iron vs. grazing in determining phytoplankton biomass in the Southern Ocean high-nutrient low-chlorophyll (HNLC) region during summer. When model simulations do not include macrozooplankton grazing explicitly, they systematically overestimate Southern Ocean chlorophyll biomass during the summer, even when there is no iron deposition from dust. When model simulations include a slow-growing macrozooplankton and trophic cascades among three zooplankton types, the high-chlorophyll summer bias in the Southern Ocean HNLC region largely disappears. Our model results suggest that the observed low phytoplankton biomass in the Southern Ocean during summer is primarily explained by the dynamics of the Southern Ocean zooplankton community, despite iron limitation of phytoplankton community growth rates. This result has implications for the representation of global biogeochemical cycles in models as zooplankton faecal pellets sink rapidly and partly control the carbon export to the intermediate and deep ocean.