title: Using Koi Carp to Produce Fish Silage

authors: Oulavallickal, Tifany

subjects: Silage

abstract: The natural environment of New Zealand is a highly cherished and important factor of the country. Introduced koi carp is considered a pest in New Zealand because it has a deleterious effect on fresh water systems. Hence eradicating the fish is essential. Identifying possible uses for this captured fish will help offset the cost of eradication. The aim of the study was to identify feasible products that could use koi carp as a raw material without the added impediment that a long term stable supply would not exist once fish numbers had been drastically reduced. The applications identified from a literature search could be categorized into three main groups: as food (for example canned carp); processed non-food uses (for example extracting fish collagen); and miscellaneous applications (such as biofertilizer). Silage production is a simple and cost effective method for using whole koi carp. The process involves mixing thawed minced fish with an acid and keeping it at a particular temperature for a short time. The effect of stirring conditions, pH and temperature was determined in the preliminary laboratory trials. A good silage requires a constant pH between 3.5 and 4.0 throughout the process and needed to be kept at 40°C for four days. Throughout the process the mixture needs to be thoroughly mixed. The main trials investigated the effect of different mineral and organic acids (singly and in combination) and the effect of using kiwifruit pulp as a source of proteolytic enzymes. The combination of hydrochloric acid and acetic acid (50:50 v/v) gave the best silage with high soluble solids content. Adding kiwifruit gave higher soluble solids after 36 h but the proteolytic activity then stopped. The process may need daily additions of green kiwifruit pulp to obtain a good silage. It is recommended that further studies on the biochemical changes during the silage process, the effect of other acid combinations in different proportions, the effect of acid strength, and other sources of exogenous proteolytic enzymes be investigated. It is also recommended that the costs of a commercial process be determined.

text: Using Koi Carp to Produce Fish Silage The natural environment of New Zealand is a highly cherished and important factor of the country. Introduced koi carp is considered a pest in New Zealand because it has a deleterious effect on fresh water systems. Hence eradicating the fish is essential. Identifying possible uses for this captured fish will help offset the cost of eradication. The aim of the study was to identify feasible products that could use koi carp as a raw material without the added impediment that a long term stable supply would not exist once fish numbers had been drastically reduced. The applications identified from a literature search could be categorized into three main groups: as food (for example canned carp); processed non-food uses (for example extracting fish collagen); and miscellaneous applications (such as biofertilizer). Silage production is a simple and cost effective method for using whole koi carp. The process involves mixing thawed minced fish with an acid and keeping it at a particular temperature for a short time. The effect of stirring conditions, pH and temperature was determined in the preliminary laboratory trials. A good silage requires a constant pH between 3.5 and 4.0 throughout the process and needed to be kept at 40°C for four days. Throughout the process the mixture needs to be thoroughly mixed. The main trials investigated the effect of different mineral and organic acids (singly and in combination) and the effect of using kiwifruit pulp as a source of proteolytic enzymes. The combination of hydrochloric acid and acetic acid (50:50 v/v) gave the best silage with high soluble solids content. Adding kiwifruit gave higher soluble solids after 36 h but the proteolytic activity then stopped. The process may need daily additions of green kiwifruit pulp to obtain a good silage. It is recommended that further studies on the biochemical changes during the silage process, the effect of other acid combinations in different proportions, the effect of acid strength, and other sources of exogenous proteolytic enzymes be investigated. It is also recommended that the costs of a commercial process be determined.

year: 2010

title: Molecular adaptations to psychrophily: the impact of ‘omic’ technologies

authors: Casanueva, Ana

subjects: molecular adaptations

abstract: The ability of cold-adapted microorganisms (generally referred to as psychrophiles) to survive is the result of molecular evolution and adaptations which, together, counteract the potentially deleterious effects of low kinetic energy environments and the freezing of water. These physiological adaptations are seen at many levels. Against a background of detailed comparative protein structural analyses, the recent surge of psychrophile proteome, genome, metagenome and transcriptome sequence data has triggered a series of sophisticated analyses of changes in global protein composition. These studies have revealed consistent and statistically robust changes in amino acid composition, interpreted as evolutionary mechanisms designed to destabilise protein structures, as well as identifying the presence of novel genes involved in cold adaptation.

text: Molecular adaptations to psychrophily: the impact of ‘omic’ technologies The ability of cold-adapted microorganisms (generally referred to as psychrophiles) to survive is the result of molecular evolution and adaptations which, together, counteract the potentially deleterious effects of low kinetic energy environments and the freezing of water. These physiological adaptations are seen at many levels. Against a background of detailed comparative protein structural analyses, the recent surge of psychrophile proteome, genome, metagenome and transcriptome sequence data has triggered a series of sophisticated analyses of changes in global protein composition. These studies have revealed consistent and statistically robust changes in amino acid composition, interpreted as evolutionary mechanisms designed to destabilise protein structures, as well as identifying the presence of novel genes involved in cold adaptation.

year: 2010

title: Phytoplankton nutrient limitation in Lake Rotorua

authors: Tempero, Grant Wayne

abstract: Lake Rotorua is one of 12 lakes jointly managed by the Rotorua Lakes Council, Te Arawa Lakes Trust and the Bay of Plenty Regional Council under the Rotorua Te Arawa Lakes Programme. The lake is currently classified as eutrophic and a Trophic Lake Index (TLI) value of 4.2 has been set as an integrated target for lake water quality. A number of catchment and lake management strategies have been implemented to achieve the targeted TLI including land use changes, wetland enhancement, lake weed harvesting, sediment detainment bunds, sewage reticulation and alum dosing. Alum (aluminium sulphate) is commonly applied to freshwater and wastewater systems to remove phosphorus, reducing its availability for phytoplankton growth. The initiation of alum dosing to the Utuhina Stream in 2006 and the Puarenga Stream in 2010 was associated with a significant decline in water column dissolved reactive phosphorus (DRP) and improvements in water quality of Lake Rotorua. 
The use of alum to control external and internal phosphorus loading has been identified as key component in the restoration of Lake Rotorua and recently observed improvements in water quality suggest that the lake could be transitioning to a more phosphorus limited state. Determination of phytoplankton nutrient limitation in Lake Rotorua was identified as a priority through the 2017 Plan Change 10 Science Review. An initial seasonal nutrient limitation study was carried out in 2019 with nutrient limitation assays conducted at 3-monthly intervals over the course of the year. Nitrogen limitation was indicated for the March assay and nutrient co-limitation for the December period, but results for the winter and spring periods were inconclusive. There has also been increasing recognition that nutrient availability in limnetic systems may vary in response to seasonal changes in external and external loading and even to isolated storm events. 
The University of Waikato was contracted to investigate potential changes in nutrient limitation within Lake Rotorua at sub-monthly time-scales, and to determine if alum dose rates could be optimised to take advantage of periods of phosphorus limitation. Phytoplankton nutrient limitation growth assays were conducted on a fortnightly basis from mid-October 2020 to May 2021. In addition to determination of lake surface nutrient and chlorophyll a concentrations, triplicate 1 L phytoplankton samples were spiked with either phosphorus (0.1 mg-P L⁻¹), nitrogen (1 mg-N L⁻¹) or phosphorus (0.1 mg-P L⁻¹) and nitrogen (1 mg-N L⁻¹) and incubated for 5-days under a single light intensity of 100 μmol m⁻²s⁻¹ PAR at lake surface temperature and photoperiod. Phytoplankton growth responses were measured as comparative chlorophyll a, comparative biomass and net biomass growth. Summarised results from the 16 assays along with the predicted nutrient state from the stoichiometric mass ratio of TN:TP are presented in the table below. 
Under the test conditions nitrogen limitation was indicated for most of the summer months (December–March) and nutrient co-limitation during the spring and late autumn. Only short (~2 weeks) periods of P-limitation were observed, one of which was associated with an intensive storm event at the end of March. These seasonal fluctuations in nitrogen and phosphorus supply are similar to those observed in other temperate limnetic systems. In the spring, external nitrogen and phosphorus loading is high, then decline in the summer as rainfall and associated inflows wane. During the summer, internal loading becomes more important in polymictic lakes due to repeated internal nutrient cycling from stratification and mixing events. This results in phosphorus limitation in the spring, transitioning to nitrogen limitation or colimitation (primarily nitrogen) in the summer, and then returning to phosphorus/colimitation during the winter due to increased nitrogen-loading from the catchment from increased catchment discharge. 
Due to the modest periods of phosphorus limitation indicated by the assays, there appears to be little potential for optimisation of alum dose rates in order capitalise on natural periods of phosphorus limitation. Further, changes in phytoplankton community composition and abundance appear to be more strongly driven by physical environmental factors such as temperature, light and wind speed, than nutrient availability. Although alum dosing is effective in removing DRP from the Utuhina and Puarenga inflows, its assumed effectiveness in reducing internal phosphorus loading in Lake Rotorua requires further evaluation.

text: Phytoplankton nutrient limitation in Lake Rotorua Lake Rotorua is one of 12 lakes jointly managed by the Rotorua Lakes Council, Te Arawa Lakes Trust and the Bay of Plenty Regional Council under the Rotorua Te Arawa Lakes Programme. The lake is currently classified as eutrophic and a Trophic Lake Index (TLI) value of 4.2 has been set as an integrated target for lake water quality. A number of catchment and lake management strategies have been implemented to achieve the targeted TLI including land use changes, wetland enhancement, lake weed harvesting, sediment detainment bunds, sewage reticulation and alum dosing. Alum (aluminium sulphate) is commonly applied to freshwater and wastewater systems to remove phosphorus, reducing its availability for phytoplankton growth. The initiation of alum dosing to the Utuhina Stream in 2006 and the Puarenga Stream in 2010 was associated with a significant decline in water column dissolved reactive phosphorus (DRP) and improvements in water quality of Lake Rotorua. 
The use of alum to control external and internal phosphorus loading has been identified as key component in the restoration of Lake Rotorua and recently observed improvements in water quality suggest that the lake could be transitioning to a more phosphorus limited state. Determination of phytoplankton nutrient limitation in Lake Rotorua was identified as a priority through the 2017 Plan Change 10 Science Review. An initial seasonal nutrient limitation study was carried out in 2019 with nutrient limitation assays conducted at 3-monthly intervals over the course of the year. Nitrogen limitation was indicated for the March assay and nutrient co-limitation for the December period, but results for the winter and spring periods were inconclusive. There has also been increasing recognition that nutrient availability in limnetic systems may vary in response to seasonal changes in external and external loading and even to isolated storm events. 
The University of Waikato was contracted to investigate potential changes in nutrient limitation within Lake Rotorua at sub-monthly time-scales, and to determine if alum dose rates could be optimised to take advantage of periods of phosphorus limitation. Phytoplankton nutrient limitation growth assays were conducted on a fortnightly basis from mid-October 2020 to May 2021. In addition to determination of lake surface nutrient and chlorophyll a concentrations, triplicate 1 L phytoplankton samples were spiked with either phosphorus (0.1 mg-P L⁻¹), nitrogen (1 mg-N L⁻¹) or phosphorus (0.1 mg-P L⁻¹) and nitrogen (1 mg-N L⁻¹) and incubated for 5-days under a single light intensity of 100 μmol m⁻²s⁻¹ PAR at lake surface temperature and photoperiod. Phytoplankton growth responses were measured as comparative chlorophyll a, comparative biomass and net biomass growth. Summarised results from the 16 assays along with the predicted nutrient state from the stoichiometric mass ratio of TN:TP are presented in the table below. 
Under the test conditions nitrogen limitation was indicated for most of the summer months (December–March) and nutrient co-limitation during the spring and late autumn. Only short (~2 weeks) periods of P-limitation were observed, one of which was associated with an intensive storm event at the end of March. These seasonal fluctuations in nitrogen and phosphorus supply are similar to those observed in other temperate limnetic systems. In the spring, external nitrogen and phosphorus loading is high, then decline in the summer as rainfall and associated inflows wane. During the summer, internal loading becomes more important in polymictic lakes due to repeated internal nutrient cycling from stratification and mixing events. This results in phosphorus limitation in the spring, transitioning to nitrogen limitation or colimitation (primarily nitrogen) in the summer, and then returning to phosphorus/colimitation during the winter due to increased nitrogen-loading from the catchment from increased catchment discharge. 
Due to the modest periods of phosphorus limitation indicated by the assays, there appears to be little potential for optimisation of alum dose rates in order capitalise on natural periods of phosphorus limitation. Further, changes in phytoplankton community composition and abundance appear to be more strongly driven by physical environmental factors such as temperature, light and wind speed, than nutrient availability. Although alum dosing is effective in removing DRP from the Utuhina and Puarenga inflows, its assumed effectiveness in reducing internal phosphorus loading in Lake Rotorua requires further evaluation.

year: 2022