Hormonal Management for the Induction of Luteolysis and Ovulation in Andalusian Jennies: Effect on Reproductive Performance, Embryo Quality and Recovery Rate

Two prostanglandins (luprostiol, LUP, and dinoprost, DIN) and two ovulation-inducing agents (human Chorionic Gonadotropin, hCG, and deslorelin, DES) were evaluated for luteolysis and estrus induction, and for ovulation induction, respectively, in embryo donor jennies. Twenty-six fertile Andalusian jennies were used. In Experiment 1, jennies (n = 112 cycles) were randomly treated with either LUP or DIN after embryo flushing. In Experiment 2, donors (n = 84 cycles) were randomly treated with either hCG or DES to induce ovulation. No differences were found between prostaglandins for all variables studied (prostaglandin–ovulation interval (POI), interovulatory interval (IOI), embryo recovery rate (ERR), positive flushing rate (PFR) and embryo grade (EG)). The ovulation rate was similar for hCG and DES (60.9% vs. 78.7%). However, the interval to ovulation (ITO) was affected (62.61 ± 7.20 vs. 48.79 ± 2.69 h). None of the other variables studied (ERR, PFR and EG) were affected (p > 0.05), except for embryo quality (p = 0.009). In short, both prostaglandins evaluated are adequate to induce luteolysis and estrus. Both ovulation-inducing agents hastened ovulation, but DES seems to be more effective than hCG. Follicular diameter affected the interval from treatment to ovulation, and high uterine edema was related to low embryo quality.

Characteristics of the Exchange Flow of the Bay of Quinte and Its Sheltered Embayments with Lake Ontario

The nature of the exchange flow between the Bay of Quinte and Lake Ontario has been studied to illustrate the effects of the seasonal onset of stratification on the flushing and transport of material within the bay. Flushing is an important physical process in bays used as drinking water sources because it affects phosphorous loads and water quality. A 2-d analytical model and a 3-dimensional numerical coastal model (FVCOM) were used together with in situ observations of temperature and water speed to illustrate the two-layer nature of the late summer exchange flow between the Bay of Quinte and Lake Ontario. Observations and model simulations were performed for spring and summer of 2018 and showed a cool wedge of bottom water in late summer extending from Lake Ontario and moving into Hay Bay at approximately 3 cm/s. Observed and modelled water speeds were used to calculate monthly averaged fluxes out of the Bay of Quinte. After the thermocline developed, Lake Ontario water backflowed into the Bay of Quinte at a rate approximately equal to the surface outflow decreasing the flushing rate. Over approximately 18.5 days of July 2018, the winds were insufficiently strong to break down the stratification, indicating that deeper waters of the bay are not well mixed. Particle tracking was used to illustrate how Hay Bay provides a habitat for algae growth within the bay.

Controlling metalimnetic bloom of Planktothrix rubescens by a novel water withdrawal strategy: a modelling study

<p>Aggregations of cyanobacteria in lakes and reservoirs are commonly associated with surface blooms, but may also occur in the metalimnion as subsurface or deep chlorophyll maxima. Metalimnetic cyanobacteria blooms are of great concern when potentially toxic species, such as Planktothrix rubescens (P. rubescens), are involved. Apparently, metalimnetic blooms of P. rubescens have increased in frequency and severity in recent years so there is a strong need to establish the external factors controlling its growth. We hypothesized that P. rubescens blooms in reservoirs can be managed by modifying the water withdrawal strategy and altering the light climate experienced by the algae. We tested our hypothesis in Rappbode Reservoir by establishing a series of withdrawal and light scenarios based on a calibrated water quality model (CE-QUAL-W2). Our scenarios demonstrated that metalimnetic water withdrawal reduced P. rubescens biomass in the reservoir. According to the simulation results we defined an optimal withdrawal volume to control P. rubescens blooms in the reservoir as approximately 10 million m<sup>3</sup> during its blooming period. The numerical results also indicated that P. rubescens growth can be most effectively suppressed if the metalimnetic withdrawal is applied in the early stage of its rapid growth (i.e. before the occurrence of blooms). Additionally, the results showed that P. rubescens biomass gradually decreased with increasing light extinction and nearly disappeared when the extinction coefficient exceeded 0.55 m<sup>-1</sup>.  Our results indicated that close linkages among in situ measurements, model simulations, empirical growth rate and flushing rate calculations could inform management strategies to minimise the harmful impacts of P. rubescens in water supplies. Such a strategy could be used in reservoir operational strategies as an adaptation way to offset the rise in P. rubescens populations that has been linked to climate change.</p>

Bivalve Mariculture in Two – Way Interaction with Phytoplankton: A Review of Feeding Mechanism and Nutrient Recycling

Bivalve mariculture is a type of molluscan farming done in open seawater on racks, rafts or longlines where naturally occurring phytoplankton serves as a key food item, introduced into the enclosures with the normal circulation of seawater. Increasingly, the reverse trophic interaction is being recognized; dissolved inorganic and organic waste compounds released by metabolically active bivalves can supply phytoplankton with nutrient and energy requirements for their growth. This two-way interaction can be viewed as a type of community symbiosis developed over long evolutionary timescales. The extent to which this affects overall nutrient budgets and thus primary production is related to the system flushing rate and residence time. Here we reviewed the feeding mechanism and nutrient recycling activities of bivalve and also emphasized the role of phytoplankton as a key nutritional live feed in sustainable bivalve mariculture. Bivalves influence nutrient dynamics through direct excretion and indirectly through microbial mediated remineralisation of their organic deposits in the sediments. The quantitative knowledge of bivalve - phytoplankton trophic interactions in coastal waters will inform bivalve mariculture development to effectively serve the needs of both seafood production and ecosystem restoration.

Eutrophication Bifurcation Analysis for Tasik Harapan Restoration

Regime shift is characterized by large, abrupt and persistent changes in ecosystem structure and dynamics. Bifurcation analysis is commonly used to identify regime shift equilibrium states and to distinguish their stability characteristics. Eutrophication in lake, a regime shift from clear-water oligotrophic state, is a stable equilibrium state that can persist for long duration. Characterized by undesirable turbid water condition, eutrophication has been known to impair valuable ecosystem services provided by lakes worldwide. The high incidence of eutrophication in Malaysian lakes (62%) mandates urgent need for lake restoration. The three-fold objectives of this paper are (1) to develop a mathematical model for analysing bifurcation criteria in regime shift, (2) to identify regime shift thresholds and (3) to propose effective ecosystem management strategy for shallow tropical lakes such as Tasik Harapan. A mathematical model consisting of four compartments: algae, phosphorus, dissolved oxygen and biochemical oxygen demand is formulated to analyse the eutrophication dynamics in the highly eutrophic Tasik Harapan (TH), a small shallow lake in Universiti Sains Malaysia (USM). Bifurcation analysis is performed by means of XPPAUT to identify the regime shift thresholds and to determine the type of lake response. Identified as irreversible, the eutrophication state of TH mandates an urgent lake restoration program to remove nutrients in the lake. Two restoration methods for reducing nutrients are assessed: (1) flushing of lake water and (2) hypothetical application of the invasive water hyacinth. Bifurcation analysis indicates that a flushing rate exceeding 0.042 day-1 is needed to restore TH to oligotrophic state. A complicated strategy of water hyacinth application would reduce the algae concentration from 300 μg/l to 120 μg/l after 9.6 years. A severe shortfall is the complicated and uncertain process of frequent removal of water hyacinth to prevent the lake from being overwhelmed by the invasive plants. The feasibility and sustainability of these two lake restoration methods are discussed. The insights gained would be useful to the relevant authorities in determining and implementing the best remediation measures for TH.

Study Of The Carrying Capacity Of The Tutud Lake, Tombatu, South-East Minahasa, For Aquaculture Production, Using [P] Parameter

The research is aimed to assess the carrying capacity of the Tutud Lake waters, to ensure a sustainable aquacutural production. The carrying capacity of the Tutud lake was assessed using the method developed by Beveridge (2004), where several parameters of water quality, aquacultural production, and the physical condition of the lake physic such as, the dimensions of the Lake, flushing rate, total phosphate [P], total aquacultural production per year and Food Conversion Ratio (FCR), were required in the assessment. Collected data were, then, analyzed using the procedures of calculation, which were combined with the several assumptions and modeling based on the previous research (Beveridge, 2004). Water sample for phosphate [P] analysis were collected four times with an interval of 7 days, and undertaken at four different positions which representing the overall water condition of the lake. Ammonia, Nitrite and Nitrate content of the waters were measured twice with an interval of 1 month. Daily fluctuation measurements were undertaken for DO, pH and temperature. Aquacultural protocols and production data were collected using questionnaire and by direct observation at the farm. The result shows that the average phosphate [P] content of the waters of Tutud lake is as high as 1,068 mg/L, which surpasses the maximum recommended value for waters used for aquacultural production. DO is at the range of 2,2 – 5,0 mg/L, while temperature ranges from 25,3oC to 29oC, and pH value varies between 6,38 and 7,89. Average Nitrite content, 0,004mg/L, and Nitrate content, 4,51mg/L, of the waters of Tutud Lake are at the safe level for aquaculture. On the contrary, Ammonia content, 0,34mg/L, and H2S content, 0,681mg/L, of the Lake are at the insecure level for aquaculture animals. Total aquacultural production per year in Tutud Lake , around 22,5 tons of fish per year, is also surpasses the carrying capacity of the waters of the Tutud Lake which is only as high as 21,48tonnes. Hence, the total production for the coming year must be reduced as many as 1,02 tones.Keywords: carrying capacity, water quality, production, Lake Tutud, TombatuABSTRAKPenelitian ini bertujuan untuk mengetahui kapasitas produksi optimal untuk menunjang aktivitas akuakultur yang berkelanjutan di danau Tutud dengan menggunakan parameter fosfor. Penelitian dilakukan di danau Tutud, Tombatu, Minahasa Tenggara, selama tiga bulan yang dimulai dari bulan September 2018 sampai bulan Januari 2019. Penentuan daya dukung untuk menunjang aktivitas akuakultur di danau Tutud menggunakan metode yang diberikan oleh Beveridge (2004), dimana dalam tahapan-tahapan prosedur penentuan daya dukung diperlukan sejumlah data menyangkut kondisi fisik danau, kandungan fosfor [P] perairan, tingkat pergantian air danau (flushing rate), produksi ikan total per tahun serta data operasional akuakultur seperti jenis pakan, jumlah pakan dan FCR. Data tersebut kemudian dianalisis menggunakan tahapan-tahapan kalkulasi yang dikombinasikan dengan beberapa asumsi hasil pemodelan penelitian sebelumnya (Beveridge, 2004). Pengambilan sampel untuk pengukuran fosfor dilakukan empat kali selama penelitian, pada empat titik yang mewakili keseluruhan danau, yaitu lokasi di dekat inlet (titik I), diluar lokasi KJT (titik II), di lokasi KJT (titik III) dan di dekat outlet (titik IV). Pengukuran fluktuasi harian dilakukan untuk parameter kualitas air DO, pH, suhu, sementara amoniak, nitrit, nitrat dan H 2 S diukur dua kali selama penelitian. Data operasional dan produksi akuakultur dikumpulkan menggunakan kuesioner serta observasi langsung.Hasil penelitian menunjukkan rataan kandungan fosfat parairan danau Tutud adalah 1,068 mg/l, sudah melewati batas maksimum baku mutu kualitas air untuk akuakultur. Hasil pengukuran untuk beberapa parameter kualitas air lainnya: DO berada pada kisaran 2,2 – 5,0 mg/l, suhu berada pada kisaran 25,30 0 C – 29 0 C, pH berada pada kisaran 6,38 – 7,89, rataan kandungan amoniak 0,34 mg/l, nitrit 0,004 mg/l , nitrat 4,51 mg/l, serta H 2 S 0,681 mg/l. Total produksi ikan per tahun di danau Tutud, sebesar 22,5 ton, sudah melebihi daya dukung perairan danau Tutud. Hasil analisis daya dukung perairan menurut Beveridge (2004), produksi akuakultur di danau Tutud harus diturunkan sebesar 1,02 ton untuk produksi tahun ke depan.Kata kunci: daya dukung, kualitas air, Produksi, Danau Tutud, Tombatu

Sunda Shelf Seas: flushing rates and residence times

The region of the Sunda Shelf has an average depth of approx. 48 m and is subject to many physical and biogeochemical processes with a strong impact from human activities. For the investigation of marine environmental water properties and quality, it is helpful to have an idea about exchange rates of water masses in the different parts of this region. Four numerical models, the global hydrodynamical model MPI-OM, the global hydrological model MPI-HM, the regional hydrodynamical model HAMSOM and a Lagrangian tracer model have been utilized to estimate the flushing rates and residence times in different seas on the Sunda Shelf. Using decadal averaged monthly transports, the commonly used flushing rate formula gives rates for the different months of approximately 40 to 70 days for the entire Sunda Shelf. For most parts of it (Malacca Strait, southern South China Sea, Java Sea), the results are similar, while for the Gulf of Thailand, the flushing rates amount to 80 to 170 days. The tracer model provides quite different but very detailed 3-D pictures with residence times of below 30 days to more than two years, depending on the location within the region, on the starting layer and on the season.