scholarly journals Links between Phenology of Large Phytoplankton and Fisheries in the Northern and Central Red Sea

2021 ◽  
Vol 13 (2) ◽  
pp. 231
Author(s):  
John A. Gittings ◽  
Dionysios. E. Raitsos ◽  
Robert J. W. Brewin ◽  
Ibrahim Hoteit
Keyword(s):  
Red Sea ◽  
Phytoplankton Bloom ◽  
Size Structure ◽  
Management Strategies ◽  
Trophic Levels ◽  
Cell Diameter ◽  
Food Web Structure ◽  
Marine Management ◽  
Fisheries Resources ◽  
Phytoplankton Size

Phytoplankton phenology and size structure are key ecological indicators that influence the survival and recruitment of higher trophic levels, marine food web structure, and biogeochemical cycling. For example, the presence of larger phytoplankton cells supports food chains that ultimately contribute to fisheries resources. Monitoring these indicators can thus provide important information to help understand the response of marine ecosystems to environmental change. In this study, we apply the phytoplankton size model of Gittings et al. (2019b) to 20-years of satellite-derived ocean colour observations in the northern and central Red Sea, and investigate interannual variability in phenology metrics for large phytoplankton (>2 µm in cell diameter). Large phytoplankton consistently bloom in the winter. However, the timing of bloom initiation and termination (in autumn and spring, respectively) varies between years. In the autumn/winter of 2002/2003, we detected a phytoplankton bloom, which initiated ~8 weeks earlier and lasted ~11 weeks longer than average. The event was linked with an eddy dipole in the central Red Sea, which increased nutrient availability and enhanced the growth of large phytoplankton. The earlier timing of food availability directly impacted the recruitment success of higher trophic levels, as represented by the maximum catch of two commercially important fisheries (Sardinella spp. and Teuthida) in the following year. The results of our analysis are essential for understanding trophic linkages between phytoplankton and fisheries and for marine management strategies in the Red Sea.

scholarly journals Remote sensing of size structure of phytoplankton communities using optical properties of the Chukchi and Bering Sea shelf region

2011 ◽  
Vol 8 (12) ◽  
pp. 3567-3580 ◽  
Author(s):  
A. Fujiwara ◽  
T. Hirawake ◽  
K. Suzuki ◽  
S.-I. Saitoh
Keyword(s):  
Remote Sensing ◽  
Optical Properties ◽  
Bering Sea ◽  
Size Structure ◽  
Trophic Levels ◽  
Ecosystem Structure ◽  
Phytoplankton Communities ◽  
Phytoplankton Size ◽  
Shelf Region ◽  
Bering Sea Shelf

Abstract. Recent ocean warming and subsequent sea ice decline resulting from climate change could affect the northward shift of the ecosystem structure in the Chukchi Sea and Bering Sea shelf region (Grebmeier et al., 2006b). The size structure of phytoplankton communities provides an index of trophic levels that is crucial to understanding the mechanisms underlying such ecosystem changes and their implications for the future. This study proposes a new ocean color algorithm for deriving this characteristic by using the region's optical properties. The size derivation model (SDM) estimates the phytoplankton size index FL on the basis of size-fractionated chlorophyll-a (chl-a) using the light absorption coefficient of phytoplankton, aph(λ), and the backscattering coefficient of suspended particles including algae, bbp(λ). FL was defined as the ratio of algal biomass attributed to cells larger than 5 μm to the total. It was expressed by a multiple regression model using the aph(λ) ratio, aph(488)/aph(555), which varies with phytoplankton pigment composition, and the spectral slope of bbp(λ), γ, which is an index of the mean suspended particle size. A validation study demonstrated that 69% of unknown data are correctly derived within FL range of ±20%. The spatial distributions of FL for the cold August of 2006 and the warm August of 2007 were compared to examine application of the SDM to satellite remote sensing. The results suggested that phytoplankton size was responsive to changes in sea surface temperature. Further analysis of satellite-derived FL values and other environmental factors can advance our understanding of ecosystem structure changes in the shelf region of the Chukchi and Bering Seas.

scholarly journals Changes in Planktivory and Herbivory Regimes in a Shallow South American Lake (Lake Blanca Chica, Argentina) Over the Last 250 Years

Water ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 597
Author(s):  
David Carrozzo ◽  
Simona Musazzi ◽  
Andrea Lami ◽  
Francisco E. Córdoba ◽  
María de los Ángeles González Sagrario
Keyword(s):  
Size Structure ◽  
Generalized Additive Models ◽  
Management Strategies ◽  
Zooplankton Community ◽  
Fish Predation ◽  
Additive Models ◽  
Fish Scales ◽  
Pheophorbide A ◽  
Food Web Structure ◽  
Species Dominance

Shallow lakes are vulnerable ecosystems impacted by human activities and climate change. The Cladocera occupy a central role in food webs and are an excellent paleoecological indicator of food web structure and trophic status. We conducted a paleolimnological study in Lake Blanca Chica (Argentina) to detect changes on the planktivory and herbivory regimes over the last 250 years. Generalized additive models were fitted to the time series of fish predation indicators (ephippial abundance and size, mucrone size, fish scales, and the planktivory index) and pheophorbide a concentration. The cladoceran assemblage changed from littoral-benthic to pelagic species dominance and zooplankton switched from large-bodied (Daphnia) to small-bodied grazers (Bosmina) ca. 1900 due to increased predation. The shift in planktivory regime (ca. 1920–1930), indicated by fish scales and the planktivory index, as well as herbivory (ca. 1920–1950), was triggered by eutrophication. Changes in planktivory affected the size structure of Bosmina, reducing its body size. This study describes the baseline for the lake as well as the profound changes in the composition and size structure of the zooplankton community due to increased predation and the shift in the planktivory regime. These findings will provide a reference status for future management strategies of this ecosystem.

scholarly journals Remotely sensing phytoplankton size structure in the Red Sea

2019 ◽  
Vol 234 ◽  
pp. 111387 ◽  
Author(s):  
John A. Gittings ◽  
Robert J.W. Brewin ◽  
Dionysios E. Raitsos ◽  
Malika Kheireddine ◽  
Mustapha Ouhssain ◽  
...  
Keyword(s):  
Red Sea ◽  
Size Structure ◽  
Phytoplankton Size ◽  
Phytoplankton Size Structure

scholarly journals Remote sensing of size structure of phytoplankton communities using optical properties of the Chukchi and Bering Sea shelf region

2011 ◽  
Vol 8 (3) ◽  
pp. 4985-5017 ◽  
Author(s):  
A. Fujiwara ◽  
T. Hirawake ◽  
K. Suzuki ◽  
S.-I. Saitoh
Keyword(s):  
Remote Sensing ◽  
Optical Properties ◽  
Bering Sea ◽  
Size Structure ◽  
Trophic Levels ◽  
Ecosystem Structure ◽  
Phytoplankton Communities ◽  
Phytoplankton Size ◽  
Shelf Region ◽  
Bering Sea Shelf

Abstract. Recent ocean warming and subsequent sea ice decline resulting from climate change could affect the northward shift of the ecosystem structure in the Chukchi Sea and Bering Sea shelf region. The size structure of phytoplankton communities provides an index of trophic levels that is crucial to understanding the mechanisms underlying such ecosystem changes and their implications for the future. This study proposes a new ocean color algorithm for deriving this characteristic by using the region's optical properties. The size derivation model (SDM) estimates the phytoplankton size index FL on the basis of size-fractionated chlorophyll-a (chl-a) using the light absorption coefficient of phytoplankton, aph(λ), and the backscattering coefficient of suspended particles including algae, bbp(λ). FL was defined as the ratio of algal biomass attributed to cells larger than 5 μm to the total. It was expressed by a multiple regression model using the aph(λ) ratio, aph(488)/aph(555), which varies with phytoplankton pigment composition, and the spectral slope of bbp(λ), γ, which is an index of the mean suspended particle size. A validation study demonstrated that the SDM successfully derived an FL value of 69 % within an error range of ± 20 % for unknown data. The spatial distributions of FL for the cold August of 2006 and the warm August of 2007 were compared to examine application of the SDM to satellite remote sensing. The results suggested that phytoplankton size was responsive to changes in sea surface temperature. Further analysis of satellite-derived FL values and other environmental factors can advance our understanding of ecosystem structure changes in the shelf region of the Chukchi and Bering Seas.

Nitrate uptake rates in freshwater plankton: the effect of food web structure

2008 ◽  
Vol 59 (8) ◽  
pp. 717 ◽  
Author(s):  
Carmen Rojo ◽  
María A. Rodrigo ◽  
Guillem Salazar ◽  
Miguel Álvarez-Cobelas
Keyword(s):  
Food Web ◽  
Nitrogen Uptake ◽  
Size Structure ◽  
Food Web Structure ◽  
Planktonic Food ◽  
Nitrogen Incorporation ◽  
Different Seasons ◽  
Effect Of Food ◽  
Phytoplankton Size ◽  
Freshwater Plankton

Nitrate incorporation rates by primary producers and the transfer of nitrogen to upper planktonic food web levels in different seasons (spring and summer of different years) were studied using a microcosm experimental approach. The study communities were natural plankton communities from Colgada Lake (central Spain), which is heavily polluted by nitrate. Natural δ15N in phytoplankton and zooplankton was measured and experiments were performed on the 15N supply. Naturally derived δ15N varied from 7.4 to 8.6‰ and from 10.0 to 16.8‰ in phytoplankton and zooplankton respectively. Nitrogen incorporation rates ranged from 0.006 to 0.036 μM h–1 and from 0.0004 to 0.0014 μM h–1 in phytoplankton and zooplankton respectively. The differences in natural δ15N levels and nitrogen incorporation rates between plankton fractions from seasonally different communities reported in the present study suggested that the nitrogen uptake by planktonic communities in Colgada Lake depend on different combinations of dominant zooplankters and phytoplankton size structure. A higher level of nitrogen uptake by phytoplankton occurred when small algae were dominant without competitors (larger algae) or main predators (herbivorous zooplankters). This was because copepods, with the lowest zooplankton nitrogen uptake, were dominant. Phytoplankton nitrogen uptake was lower when big algae were dominant.

Size-fractionated surface phytoplankton in the Kara and Laptev Seas: environmental control and spatial variability

2021 ◽  
Vol 664 ◽  
pp. 59-77
Author(s):  
AB Demidov ◽  
IN Sukhanova ◽  
TA Belevich ◽  
MV Flint ◽  
VI Gagarin ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Primary Production ◽  
Water Temperature ◽  
Environmental Control ◽  
Size Structure ◽  
Total Carbon ◽  
The Arctic ◽  
Size Groups ◽  
Phytoplankton Size ◽  
Phytoplankton Size Structure

Climate-induced variability of phytoplankton size structure influences primary productivity, marine food web dynamics, biosedimentation and exchange of CO2 between the atmosphere and ocean. Investigation of phytoplankton size structure in the Arctic Ocean is important due to rapid changes in its ecosystems related to increasing temperature and declining sea ice cover. We estimated the contribution of surface micro-, nano- and picophytoplankton to the total carbon biomass, chlorophyll a concentration and primary production in the Kara and Laptev Seas and investigated the relationships of these phytoplankton size groups with environmental factors which determine their spatial variability. Additionally, we compared chlorophyll specific carbon fixation rate, specific growth rate and carbon to chlorophyll ratios among different phytoplankton size groups. The investigation was carried out from August to September 2018. Generally, picophytoplankton was dominant in terms of chlorophyll a and primary production in the whole study area. The spatial variability of phytoplankton size classes was influenced by river discharge and relied mainly on water temperature, salinity and dissolved silicon concentration. Microphytoplankton prevailed across the river runoff region under conditions of low salinity and relatively high water temperature, while picophytoplankton was predominant under conditions of high salinity and low water temperature. Our study is the first to characterize size-fractionated phytoplankton abundance in the Kara and Laptev Seas, and provides a baseline for future assessment of the response of Kara and Laptev Sea ecosystems to climate-induced processes using phytoplankton size structure.

scholarly journals Mesoscale variations in the assemblage structure and trophodynamics of mesozooplankton communities of the Adriatic basin (Mediterranean Sea)

2021 ◽  
Author(s):  
Emanuela Fanelli ◽  
Samuele Menicucci ◽  
Sara Malavolti ◽  
Andrea De Felice ◽  
Iole Leonori
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Mediterranean Sea ◽  
Environmental Variables ◽  
Complex Structure ◽  
Assemblage Structure ◽  
Trophic Levels ◽  
Ecosystem Functions ◽  
Food Web Structure ◽  
Adriatic Basin

Abstract. Zooplankton are critical to the functioning of ocean food webs because of their utter abundance and vital ecosystem roles. Zooplankton communities are highly diverse and thus perform a variety of ecosystem functions, thus changes in their community or food web structure may provide evidence of ecosystem alteration. Assemblage structure and trophodynamics of mesozooplantkon communities were examined across the Adriatic basin, the northernmost and most productive basin of the Mediterranean Sea. Samples were collected in June–July 2019 along coast-offshore transects covering the whole western Adriatic side, consistently environmental variables were also recorded. Results showed a clear separation between samples from the northern-central Adriatic and the southern ones, with a further segregation, although less clear, of inshore vs. off-shore stations, the latter mostly dominated in the central and southern stations by gelatinous plankton. Such patterns were mainly driven by chlorophyll-a concentration (as a proxy of primary production) for northern-central stations, i.e. closer to the Po river input, and by temperature and salinity, for southern ones, with the DistLM model explaining 46 % of total variance. The analysis of stable isotopes of nitrogen and carbon allowed to identify a complex food web characterized by 3 trophic levels from herbivores to carnivores, passing through the mixed feeding behavior of omnivores, shifting from phytoplankton/detritus ingestion to microzooplankton. Trophic structure also spatially varied according to sub-area, with the northern-central sub-areas differing from each other and from the southern stations. Our results highlighted the importance of environmental variables as drivers of zooplanktonic communities and the complex structure of their food webs. Disentangling and considering such complexity is crucial to generate realistic predictions on the functioning of aquatic ecosystems, especially in high productive and, at the same time, overexploited area such as the Adriatic Sea.

scholarly journals PENGELOLAAN PERIKANAN TANGKAP DI KAWASAN TAMAN NASIONAL KARIMUNJAWA Management of Capture fisheries in the Area of Karimunjawa National Park

2019 ◽  
Vol 8 (2) ◽  
pp. 102-110
Author(s):  
Yulia Santi ◽  
Sutrisno Anggoro ◽  
Suryanti Suryanti
Keyword(s):  
National Park ◽  
Descriptive Analysis ◽  
Management Strategies ◽  
Literature Study ◽  
Purposive Sampling ◽  
Fisheries Resources ◽  
Management Institutions ◽  
And Training

ABSTRAKPerikanan  tangkap  di  kawasan  Taman  Nasional  Karimunjawa  dikelola  oleh  lebih  dari  satu  instansipengelola.  Setiap  instansi  diduga  mempunyai  peran  masing-  masing  sesuai  tupoksinya.  Saat  ini  belum diketahui secara nyata instansi apa saja yang mengelola beserta perannya. Tujuan penelitian ini adalah untuk mengidentifikasi instansi pengelola yang berperan dalam pengelolaan perikanan tangkap di kawasan TNKJ, persepsi,  aspirasi  dan  partisipasi  nelayan  terhadap  pengelolaan  perikanan  tangkap  serta  bagaimana  strategi pengelola  dalam  pengawasan  perikanan  tangkap.  Metode  penelitian  ini  adalah  studi  kasus  dengan  analisis deskriptif, dimana pengumpulan data melalui wawancara dan studi pustaka. Penentuan responden menggunakan metode purposive sampling, responden terdiri dari nelayan dan instansi pengelola. Hasil penelitian menunjukan bahwa  instansi yang  mengelola  perikanan tangkap adalah Unit  Pelaksana  Teknis   Pelabuhan Perikanan Pantai Karimunjawa, Balai Taman Nasional Karimunjawa, Dinas Perikanan, Polisi Air   dan Tentara Nasional Indonesia Angkatan Laut dan Satuan Kerja Pengawasan Sumberdaya Kelautan dan   Perikanan. Pembagian peran masing- masing instansi pengelola sudah sesuai dengan bidang masing-masing  serta tidak terjadi tumpang tindih kewenangan. Sinkronisasi dan koordinasi sudah dilakukan, hal ini terbukti   dengan  adanya  Nota  Kesepakatan Bersama. Sebanyak 80% nelayan setuju dengan peraturan yang diterapkan. Partisipasi nelayan terhadap sosialisasi dan pelatihan rendah yaitu 35% dan 19%. Strategi pengelola dalam pengawasan perikanan tangkap adalah dengan membentuk dan memberdayakan Pengawas   Perikanan  dan  Kelompok  Masyarakat  Pengawas  secara  sinergi. Strategi untuk  meningkatkan partisipasi  nelayan  dalam  sosialisasi  dan  pelatihan  adalah  dengan  memberikan penyadaran  motivasi dan  apresiasi berupa penghargaan dan pendampingan. ABSTRACTCapture   fisheries   in Karimunjawa National   Park   are   managed by   more   than one   management institutions.  Each  institution  is  assumed  to  have  their  respective  roles  according  to  their  basic  tasks  andfunctions. It is not yet known exactly what institutions are managing along with their roles. The purposes of  this study  were to know what institutions  were involved  in the management of capture fisheries in TNKJ  areas, perceptions, aspirations and participation of fishermen on the management of capture fisheries and  how the management strategy in the supervision of capture fisheries. This research method was case study with descriptive analysis, where data collected by interview and literature study. Determination of  respondents used purposive sampling method, respondents consist of fishermen and manager institution. The results showed that the institutions that managed capture fisheries were Technical Implementation Unit  Karimunjawa Fishery Port, Karimunjawa National Park Office, Fisheries Official, Water Police and Indonesian National Army – Navy and Work Unit of Supervision of Marine and Fisheries Resources. The  division of roles of each institution agency was in accordance with their respective fields and there was no  overlapping authority. Synchronization and coordination had been done, it was proved by the Memorandum of Understanding (MoU). As many as 80% of fishermen agree with the regulations applied. The  participations of fishermen on socialization and training were low at 35% and 19%. The management strategies in the supervision of capture fisheries were by establishing and empowering Fisheries Supervisor  and a group of supervisor community (PokMasWas). The strategies to increase the participation of fishermen in socialization and training were by giving awareness of motivation and appreciation in the form  of recognition and assistance.

Balancing Fisheries Management and Water Uses for Impounded River Systems

2008 ◽  
Keyword(s):  
Size Structure ◽  
Management Strategies ◽  
Historical Context ◽  
Lepomis Macrochirus ◽  
Large Body ◽  
Early Maturation ◽  
Reservoir Species ◽  
Clear Identification ◽  
Management Approaches ◽  
Underlying Mechanisms

<em>Abstract</em>.—Although stunting is a fairly common phenomenon in fishes, confusion remains about underlying mechanisms and appropriate management strategies. Herein, I summarize current literature to provide a synthetic look at factors that can cause stunting and consider associated management strategies. First, I provide historical context by reviewing early literature, much of which is focused on density-dependent slow growth as the cause of stunting. A brief summary of more recent literature, however, suggests that stunting is often more complex than early investigations might indicate, and mechanisms such as early maturation and overexploitation of adults are considered. Because the bluegill <em>Lepomis macrochirus </em>is an extremely common reservoir species, a large body of literature related to its population size structure and associated management strategies is available. Therefore, I use bluegill as a model system to describe how various mechanisms might lead to stunting and indicate important considerations from a management standpoint. In the final section, I review management strategies and argue, among other things, that consistent language, clear identification of underlying mechanisms, and multifaceted management approaches are necessary for robust results when dealing with stunted populations.

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