title: Is fish food from aquarium suppliers a vector for non-native zooplankton to New Zealand?

authors: Mahaarachchige, Buddhika Udayangani Perera

subjects: Artemia

abstract: There have been a number of recent records of non-native zooplankton invasions in New Zealand, but the transport vectors leading to their introduction are not well understood.  Commercially available fish foods containing zooplankton are widely used in home aquariums and the aquaculture industry. These foods are either imported to, or cultured within, New Zealand, and sold as freeze-dried, sun-dried or frozen adults, as capsulated or decapsulated cysts, or as live individuals. In this study, fish food containing Daphnia O.F. Müller, 1785  (Cladocera), Artemia (brine shrimp) and Brachionus (rotifers) were bought from a variety of commercial suppliers within the North Island, New Zealand, which were cultured and manufactured domestically or internationally. Live Daphnia samples were identified morphologically and were found to contain a variety of both native and non-native Daphnia species, as well as copepods, ostracods, rotifers and other non-Daphnia cladoceran species. Freeze-dried and sun-dried diapausing eggs of Daphnia and the rotifer Brachionus were incubated in artificial pond water, Aachener Daphnien Medium (ADaM) and filtered pond water, but hatching of these were unsuccessful. In contrast, Artemia bought as both capsulated and decapsulated cysts were successfully hatched in water with a salinity of 25 ppt and temperatures of 20 °C. The resulting Artemia populations were either parthenogenic or sexual, varying by manufacturer. Frozen whole adult Artemia were found to carry eggs but could not be hatched. Due to the risk of misidentifications from morphological identification, a 658-bp fragment from the 5ʹ region of the COI gene was amplified from tissue samples. The phylogenetic tree constructed from the COI gene sequences identified distinct clades corresponding to four species: A. franciscana, A. parthenogenetica (both hatched from eggs as viable populations), A. sinica, and A. salina (both identified in food, but not viable). The BLAST analysis indicated that the capsulated  cysts from USA and German manufacturers contained Artemia franciscana, while the Chinese supply contained A. parthenogenetica. Decapsulated cysts from a Chinese manufacturer hatched into A. parthenogenetica. While A. franciscana can be legally imported into New Zealand, A. parthenogenetica is not listed in the Import Health Standard for ‘Fish food and fish bait’ under the Biosecurity Act 1993. The morphological identifications matched the BLAST analysis data for Daphnia. Non-native Daphnia pulex was recorded from live samples from Te Aroha, Hamilton and Wellington (LID5). An Auckland sample and another Wellington sample comprised of native D. carinata s.l. Overall, commercially available fish food from aquarium suppliers can act as a vector for non-native zooplankton to New Zealand.

text: Is fish food from aquarium suppliers a vector for non-native zooplankton to New Zealand? There have been a number of recent records of non-native zooplankton invasions in New Zealand, but the transport vectors leading to their introduction are not well understood.  Commercially available fish foods containing zooplankton are widely used in home aquariums and the aquaculture industry. These foods are either imported to, or cultured within, New Zealand, and sold as freeze-dried, sun-dried or frozen adults, as capsulated or decapsulated cysts, or as live individuals. In this study, fish food containing Daphnia O.F. Müller, 1785  (Cladocera), Artemia (brine shrimp) and Brachionus (rotifers) were bought from a variety of commercial suppliers within the North Island, New Zealand, which were cultured and manufactured domestically or internationally. Live Daphnia samples were identified morphologically and were found to contain a variety of both native and non-native Daphnia species, as well as copepods, ostracods, rotifers and other non-Daphnia cladoceran species. Freeze-dried and sun-dried diapausing eggs of Daphnia and the rotifer Brachionus were incubated in artificial pond water, Aachener Daphnien Medium (ADaM) and filtered pond water, but hatching of these were unsuccessful. In contrast, Artemia bought as both capsulated and decapsulated cysts were successfully hatched in water with a salinity of 25 ppt and temperatures of 20 °C. The resulting Artemia populations were either parthenogenic or sexual, varying by manufacturer. Frozen whole adult Artemia were found to carry eggs but could not be hatched. Due to the risk of misidentifications from morphological identification, a 658-bp fragment from the 5ʹ region of the COI gene was amplified from tissue samples. The phylogenetic tree constructed from the COI gene sequences identified distinct clades corresponding to four species: A. franciscana, A. parthenogenetica (both hatched from eggs as viable populations), A. sinica, and A. salina (both identified in food, but not viable). The BLAST analysis indicated that the capsulated  cysts from USA and German manufacturers contained Artemia franciscana, while the Chinese supply contained A. parthenogenetica. Decapsulated cysts from a Chinese manufacturer hatched into A. parthenogenetica. While A. franciscana can be legally imported into New Zealand, A. parthenogenetica is not listed in the Import Health Standard for ‘Fish food and fish bait’ under the Biosecurity Act 1993. The morphological identifications matched the BLAST analysis data for Daphnia. Non-native Daphnia pulex was recorded from live samples from Te Aroha, Hamilton and Wellington (LID5). An Auckland sample and another Wellington sample comprised of native D. carinata s.l. Overall, commercially available fish food from aquarium suppliers can act as a vector for non-native zooplankton to New Zealand.

year: 2025

title: The influence of sediment nutrient dynamics on the response of lake ecosystems to restoration and climate change

authors: Trolle, Dennis

subjects: Sediment

abstract: Human activities such as urban settlement, farming, forestry and recreation, have caused deterioration of water quality in many freshwater lakes worldwide. Apart from anthropogenic impacts, it is also recognized that climate has a direct influence on lake water temperature, nutrient loads, phytoplankton abundance and chemistry. However, little is known about the potential effects of future climate change on lake water quality. Understanding the dynamics, abundance and availability of nutrient pools in lake bottom sediments is fundamentally important for predicting how, and over what time-scales, lake ecosystems will respond to future scenarios such as climate change, in-lake restoration or altered external nutrient loading. Through a sediment field study on 14 different lakes, and applications of complex lake ecosystem models to three New Zealand lakes, this study examined the spatial and temporal dynamics of sediment nutrient concentrations, and made considerations of the effects of restoration measures and future climate change on lake water quality.

To gain insight into processes influencing the dynamics of horizontal and vertical gradients of sediment nutrient concentrations, intact sediment cores were collected from twelve lakes within the Bay of Plenty province, North Island of New Zealand. In addition, intact sediment cores were collected from shallow Lake Te Waihora (Ellesmere) in the Canterbury province, South Island of New Zealand and shallow Lake Taihu in the Jaingsu province, China. The observed vertical concentration profiles of total phosphorus (TP) in the sediments revealed that the shape of these profiles can be similar across gradients of widely differing trophic status. Empirical and mechanistic steady state profile models were derived to describe the vertical distribution of total carbon (TC), total nitrogen (TN) and TP concentrations in the sediments. These models revealed that density-driven burial and biodiffusive mixing, which in the models also includes effects of redox-driven gradients, are strongly correlated with vertical gradients of sediment TC, TN and TP content, whereas lake trophic status was not.

Despite enhancing knowledge of the processes influencing vertical gradients of sediment nutrient concentrations, little is known about the rates at which sediment nutrient concentrations may change as a response to changes in external loading or climate. Studies into the composition of bottom sediments have been undertaken intermittently over the past three decades for the 12 lakes in the Bay of Plenty. These studies, together with the data collected in this study, were used to quantify temporal changes in sediment chemistry across the lakes. Comparison of the data collected in this study with results from a survey in 1995 showed that surficial sediment (0-2 cm) TP concentrations have increased in three of the 12 lakes, at rates ranging from 27.5 to 114.4 mg P kg-1 dry wt yr-1. TN concentrations in surficial sediments have increased in nine of the 12 lakes at rates ranging from 51.8 to 869.2 mg N kg-1 dry wt yr-1. A correlation analysis revealed that temporal changes in sediment TP and TN concentrations were not significantly linearly related (pgt0.05) to catchment area or temporal changes of different water column indices considered to reflect lake trophic state, including annual mean water column concentrations of TP, TN or chlorophyll a (Chl a).

While vertical profiles of sediment nutrient concentrations can be used to provide information about historical changes of trophic status in lakes, little is known about horizontal variability of sediment nutrient concentrations, including possibly relationships with horizontal variations in water column variables. In the large, shallow and eutrophic Lake Taihu, China, there are distinct horizontal water column concentration gradients of nutrients and Chl a. Concentrations are generally high in the north, where some of the major polluted tributaries enter the lake, and relatively low in the south, where macrophytes generally are abundant. To test whether these water column concentration gradients are similarly reflected in spatial heterogeneity of nutrient concentrations within the bottom sediments of Lake Taihu, I examined correlations between concentrations of TP and TN in surficial sediments (0-2 cm) and TP, TN and Chl a concentrations in water column samples determined for 32 sites in 2005. Linear correlation analysis revealed that surficial sediment TP concentrations across the 32 stations were related significantly, though weakly, to annual mean water column concentrations of TP and TN as well as Chl a. Correlations of surficial sediment TN with water column variables were, however, not significant (p gt 0.05).
To better understand the effects of future climate change on lakes of different trophic status, I applied the one-dimensional lake ecosystem model, DYRESM-CAEDYM, to oligo-mesotrophic Lake Okareka, eutrophic Lake Rotoehu and highly eutrophic Lake Te Waihora. All three models were calibrated based on a three-year period (July 2002 - June 2005) and validated on a separate two-year period (July 2005 - June 2007). The model simulations generally showed good agreement with observed data for temperature, dissolved oxygen (DO), and total nutrient and Chl a concentrations. To represent a possible future climate of 2100, temperature predictions were derived from the regional climate model, DARLAM, based on the Intergovernmental Panel on Climate Change (IPCC) A2 scenario, which suggests that air temperatures by the year 2100 will increase by an average of 2.5 'C and 2.7 'C for the Bay of Plenty and the Canterbury province, respectively, relative to the base scenario (years 2002-2007). Model simulations of the future climate scenarios indicate that climatic changes generally will lead to a degradation of lake water quality in all three lakes, especially during summer months, and further suggest that the effects on annual mean surface concentrations of TP, TN and Chl a will be equivalent to an increase in external TN and TP loading by 25-50%. Simulations for Lake Rotoehu, where diatoms and cyanophytes were represented in the conceptual model, further suggest that cyanophytes will be more abundant in the future, increasing by gt15% in annual mean biomass. Although the effects of climate change may be delayed or slightly mediated by the chemical resilience of the sediment nutrient pools, the effects of climate change on lake water quality in the New Zealand lakes will be of a magnitude that should be considered as management strategies are planned and implemented, thus increasing the probability of successful preservation or improvement in water quality in future decades.

text: The influence of sediment nutrient dynamics on the response of lake ecosystems to restoration and climate change Human activities such as urban settlement, farming, forestry and recreation, have caused deterioration of water quality in many freshwater lakes worldwide. Apart from anthropogenic impacts, it is also recognized that climate has a direct influence on lake water temperature, nutrient loads, phytoplankton abundance and chemistry. However, little is known about the potential effects of future climate change on lake water quality. Understanding the dynamics, abundance and availability of nutrient pools in lake bottom sediments is fundamentally important for predicting how, and over what time-scales, lake ecosystems will respond to future scenarios such as climate change, in-lake restoration or altered external nutrient loading. Through a sediment field study on 14 different lakes, and applications of complex lake ecosystem models to three New Zealand lakes, this study examined the spatial and temporal dynamics of sediment nutrient concentrations, and made considerations of the effects of restoration measures and future climate change on lake water quality.

To gain insight into processes influencing the dynamics of horizontal and vertical gradients of sediment nutrient concentrations, intact sediment cores were collected from twelve lakes within the Bay of Plenty province, North Island of New Zealand. In addition, intact sediment cores were collected from shallow Lake Te Waihora (Ellesmere) in the Canterbury province, South Island of New Zealand and shallow Lake Taihu in the Jaingsu province, China. The observed vertical concentration profiles of total phosphorus (TP) in the sediments revealed that the shape of these profiles can be similar across gradients of widely differing trophic status. Empirical and mechanistic steady state profile models were derived to describe the vertical distribution of total carbon (TC), total nitrogen (TN) and TP concentrations in the sediments. These models revealed that density-driven burial and biodiffusive mixing, which in the models also includes effects of redox-driven gradients, are strongly correlated with vertical gradients of sediment TC, TN and TP content, whereas lake trophic status was not.

Despite enhancing knowledge of the processes influencing vertical gradients of sediment nutrient concentrations, little is known about the rates at which sediment nutrient concentrations may change as a response to changes in external loading or climate. Studies into the composition of bottom sediments have been undertaken intermittently over the past three decades for the 12 lakes in the Bay of Plenty. These studies, together with the data collected in this study, were used to quantify temporal changes in sediment chemistry across the lakes. Comparison of the data collected in this study with results from a survey in 1995 showed that surficial sediment (0-2 cm) TP concentrations have increased in three of the 12 lakes, at rates ranging from 27.5 to 114.4 mg P kg-1 dry wt yr-1. TN concentrations in surficial sediments have increased in nine of the 12 lakes at rates ranging from 51.8 to 869.2 mg N kg-1 dry wt yr-1. A correlation analysis revealed that temporal changes in sediment TP and TN concentrations were not significantly linearly related (pgt0.05) to catchment area or temporal changes of different water column indices considered to reflect lake trophic state, including annual mean water column concentrations of TP, TN or chlorophyll a (Chl a).

While vertical profiles of sediment nutrient concentrations can be used to provide information about historical changes of trophic status in lakes, little is known about horizontal variability of sediment nutrient concentrations, including possibly relationships with horizontal variations in water column variables. In the large, shallow and eutrophic Lake Taihu, China, there are distinct horizontal water column concentration gradients of nutrients and Chl a. Concentrations are generally high in the north, where some of the major polluted tributaries enter the lake, and relatively low in the south, where macrophytes generally are abundant. To test whether these water column concentration gradients are similarly reflected in spatial heterogeneity of nutrient concentrations within the bottom sediments of Lake Taihu, I examined correlations between concentrations of TP and TN in surficial sediments (0-2 cm) and TP, TN and Chl a concentrations in water column samples determined for 32 sites in 2005. Linear correlation analysis revealed that surficial sediment TP concentrations across the 32 stations were related significantly, though weakly, to annual mean water column concentrations of TP and TN as well as Chl a. Correlations of surficial sediment TN with water column variables were, however, not significant (p gt 0.05).
To better understand the effects of future climate change on lakes of different trophic status, I applied the one-dimensional lake ecosystem model, DYRESM-CAEDYM, to oligo-mesotrophic Lake Okareka, eutrophic Lake Rotoehu and highly eutrophic Lake Te Waihora. All three models were calibrated based on a three-year period (July 2002 - June 2005) and validated on a separate two-year period (July 2005 - June 2007). The model simulations generally showed good agreement with observed data for temperature, dissolved oxygen (DO), and total nutrient and Chl a concentrations. To represent a possible future climate of 2100, temperature predictions were derived from the regional climate model, DARLAM, based on the Intergovernmental Panel on Climate Change (IPCC) A2 scenario, which suggests that air temperatures by the year 2100 will increase by an average of 2.5 'C and 2.7 'C for the Bay of Plenty and the Canterbury province, respectively, relative to the base scenario (years 2002-2007). Model simulations of the future climate scenarios indicate that climatic changes generally will lead to a degradation of lake water quality in all three lakes, especially during summer months, and further suggest that the effects on annual mean surface concentrations of TP, TN and Chl a will be equivalent to an increase in external TN and TP loading by 25-50%. Simulations for Lake Rotoehu, where diatoms and cyanophytes were represented in the conceptual model, further suggest that cyanophytes will be more abundant in the future, increasing by gt15% in annual mean biomass. Although the effects of climate change may be delayed or slightly mediated by the chemical resilience of the sediment nutrient pools, the effects of climate change on lake water quality in the New Zealand lakes will be of a magnitude that should be considered as management strategies are planned and implemented, thus increasing the probability of successful preservation or improvement in water quality in future decades.

year: 2009

title: The importance of whakapapa for understanding fertility

authors: Rarere, Moana

abstract: The Māori fertility transition—which saw a shift from high to low birth rates between 1966 to 1976—was one of the most rapid fertility declines observed anywhere in the world. Since then, Māori fertility has hovered around replacement level (2.1 births per woman), somewhat above that of Pākehā (European) New Zealanders. More striking are differences in timing with Māori women bearing their children younger and over a longer duration. This paper sits within a broader research project that asks: What are the important influences that have sustained contemporary Māori fertility patterns? Drawing on Mana Wahine (Māori women’s discourses) and whakawhiti kōrero (interviews) with wāhine Māori (Māori women) this paper highlights whakapapa (genealogy) as an important concept in broadening and deepening our understandings of fertility, and situating individual fertility and reproduction within a broader set of relations.

text: The importance of whakapapa for understanding fertility The Māori fertility transition—which saw a shift from high to low birth rates between 1966 to 1976—was one of the most rapid fertility declines observed anywhere in the world. Since then, Māori fertility has hovered around replacement level (2.1 births per woman), somewhat above that of Pākehā (European) New Zealanders. More striking are differences in timing with Māori women bearing their children younger and over a longer duration. This paper sits within a broader research project that asks: What are the important influences that have sustained contemporary Māori fertility patterns? Drawing on Mana Wahine (Māori women’s discourses) and whakawhiti kōrero (interviews) with wāhine Māori (Māori women) this paper highlights whakapapa (genealogy) as an important concept in broadening and deepening our understandings of fertility, and situating individual fertility and reproduction within a broader set of relations.

year: 2022