Please enable JavaScript.

Coggle requires JavaScript to display documents.

Relationship between DIN and macroinvertebrates (Changes in…

- - - - attempts to link the MCI to instream nitrogen availability in Canterbury have comprehensively demonstrated the lack of a simple or direct relationship (Moore, 2014).
    - - TR no relationship with nutrients
    - - Abundance and composition of periphyton and benthic macroinvertebrates were treated as potential nutrient response variables for 74 streams in montane Colorado. The streams ranged from unenriched to mildly enriched with nutrients (N, P).
        
        Nutrient concentrations were also unrelated to periphyton and macroinvertebrate richness, diversity and community composition. Macroinvertebrate communities did, however, show a strong positive relationship to periphyton abundance
      - Lewis and McCutchan (2010) also reported no
        significant relationship between nutrients and macroinvertebrate
        abundance in river data collected in Colorado, but this study did not include sites that were substantially polluted with nutrients, and the results were acknowledged to be only applicable to nutrient concentrations arising from natural variability and mild anthropogenic enrichment.
    - - A contrasting view of the utility of macroinvertebrates for these
        purposes is provided by Friberg et al. (2010) based on analysis of
        presence–absence macroinvertebrate data from Danish rivers. Although negative responses to total phosphorus and ammoniacal nitrogen were found, no relationship was found with total nitrogen, leading to the conclusion that macroinvertebrates are poor indicators of eutrophication. However this may have been more a consequence of being unable to detect changes in abundance, and the relatively small range of taxa which included few grazers, unlike the study of Smith et al. (2007).
  - - - Nitrate enrichment stimulated decomposition of oak leaves and balsa veneers, fungal biomass accrual on alder leaves and balsa veneers and sporulation of aquatic hyphomycetes on all substrates
        
        *abundances or richness of litter-associated invertebrates were not affected by nitrate addition*
        
        It appears that microbial nitrogen demands can be met at relatively low levels of dissolved nitrate, suggesting that even minor increases in nitrogen in streams due to, e.g., anthropogenic eutrophication may lead to significant shifts in microbial dynamics and ecosystem functioning.
- - - - Hill, W. R. and Griffiths, N. A. (2017
        
        Snails assimilated and excreted up to 50% of the nitrogen initially taken up by autotrophs and leaf microbes, and they were likely to have additional effects on nitrogen spiraling through egestion and the cropping of assimilative biomass.
        
        3.Snails were less important as nitrogen sinks than as sources of recycled nitrogen in Walker Branch. Over the course of the year, snails excreted approximately 12 times more nitrogen than they accumulated in biomass
        
        Primary consumers like Elimia are important catalysts of nutrient movement through headwater streams, decreasing residence times and facilitating fluxes to downstream waters.
    - - Recently, several studies have been published which tested conceptual models on effects of N deposition in food webs, focusing on changes in plant-herbivore relations after releasing primary producers fromN-limitation and altering foliage N content, including consequences for predatory species (Meunier et al., 2016; Pöyry et al., 2016). Comparable to the review on chemical stress (Camargo and Alonso, 2006), they identify possible causal mechanisms by which fauna is affected. However, these studies also show a lack of experimental data and cover only a limited part of this ecologically complex subject.
        
        Also: David R. Lenat,
        J. Kent Crawford
        (1994)
        
        nutrient concentrations were highest at the agricultural site, and the amount of ‘available’ dissolved nitrogen was elevated at both the urban and agricultural sites. Invertebrate taxa richness, a biotic index, and the number of unique invertebrate species (found at only one site) indicated moderate stress (Fair water quality) at the agricultural site
    - - Like a decrease in habitat and flow conditions the decrease of resource abundance due to DIN increases is very likely, but again causal evidence on the relationship between N deposition and the decrease of plant-dependent animal species hardly occurs
  - - - Predators and parasitoids depend for their food on the presence of sufficient prey items or hosts
      - Cashman, M. J., et al. (2013).
        
        The biochemical composition of primary food resources may affect secondary production, growth, reproduction and other physiological responses in consumers and may be an important driver of food-web dynamics. Changes in land use, riparian clearing and non-point nutrient inputs to streams have the potential to alter the biochemical composition of periphyton, and characterising this relationship may be critical to understand the processes by which environmental change can affect food webs and ecosystem function.
        
        4.Results from this study suggest that increased light and nutrients, a condition common in urban and agricultural catchments, would increase 18C PUFA intermediates that would be available in periphyton food sources, but decrease the availability of essential 20-22C HUFAs. If stream consumers are unable to elongate polyunsaturated fatty acids (PUFAs PUFAs into essential Highly UFAs, there may be important effects on food webs, including shifts by invertebrate consumers from herbivory to omnivory or carnivory, or changes in the species composition of aquatic consumers.
    - - Leaflitter
        decomposition decreased in atmospherically acidified
        woodland streams because of the negative effects on microbial
        decomposers (bacteria and fungi), with aquatic invertebrates
        (detritivore species, mainly) being affected due to changes in food
        quality and in food availability (Hildrew et al., 1984; Chamier,
        1987; Groom and Hildrew, 1989; Griffith and Perry, 1994;
        Dangles et al., 2004).
  - - - Presence or absence of cover was the primary determinant of what invertebrate taxa dominated in the baskets, most likely as a result of differences in food resources. The filter feeding Coloburiscus humeralis dominated numerically in the covered baskets, whereas the generalist grazers Deleatidium spp., Beraeoptera roria, Orthocladiinae, and Diamesinae dominated numerically in the open baskets. However, cover had no effect on the overall abundance and species richness of the experimental baskets but disturbance reduced abundance and to a lesser extent species richness.
- - - - Therefore, mechanisms behind effects of N deposition on animal species and diversity remain unclear, which hampers optimisation of nature restoration and conservation measures
- - - - Elevated concentrations of DRP and dissolved
        inorganic nitrogen (NO3-N and NH4-N) may induce
        excessive growths of macrophytes that retard water
        flows and require periodic clearance, such as by
        draglining (Smith et al. 1993).
    - - The overall structure of invertebrate assemblages appeared to be influenced by a combination of regional differences in substrate type, nutrient concentrations, water clarity, and macrophyte cover
- - - - Can cause chemical stress directly to invertebrates or impact and alter habitat and flow conditions:
        it can stimulate or enhance the development, maintenance and proliferation of primary producers, resulting in eutrophication of aquatic ecosystems; (3) it can reach toxic levels that impair the ability of aquatic animals to survive, grow and reproduce
  - - - But no control of other variables. Why N over another?
        
        However, because DIN and TN, DRP
        and TP, as well as TSS and turbidity were highly corre-
        lated with each other (Table 2), only the higher- ranking
        nitrogen, phosphorus, or suspended ﬁne sediment
        attribute was included in the ﬁnal analysis, respectively
      - Macroinvertebrate and periphyton assemblage turnover was most prominent relative to elsewhere across the entire gra-
        dient at the low end of the N gradient spanning from the
        lowest observed concentrations (0.06 mg TN/L, 0.01 mg
        DIN/L) up to about 0.5 mg TN/L for macroinvertebrates
        and 0.3 mg DIN/L for periphyton
        
        But, they go on to say: Hence, compared to periphyton composi-
        tional turnover, the mechanisms underlying the turnover
        of macroinvertebrate assemblages are more complex
        since the species- speciﬁc responses to increasing N supply
        could be a result of sensitivities to one or multiple envi-
        ronmental effects of eutrophication in addition to inter-
        species interactions as well as due to direct toxic effects
        
        Levels below nitrate toxicity guidelines suggested for freshwater aquatic species in New Zealand Hickey and Martin 2009 = 1.7 mg NO3-N/L for Environments which are
        subjected to a range of
        disturbances from human
        activity.
      - Threshold implies causative
  - - - More tolerant species found in pasture than native streams
      - Other studies have also reported greater densities and biomasses in streams with high nutrients compared to pristine streams (Quinn and others 1997),
  - - - Aggregate macroinvertebrate biomass was predicted by watershed % impervious surface cover (ISC) (–), conductivity and nutrient concentrations
  - - - TN is probably
        the better indicator of ecosystem trophic state than
        DIN (Dodds 2003), so our results suggest that indirect effects
        on macroinvertebrate communities via the eutrophication
        pathway are more likely than direct toxicity effects
        of dissolved N compounds. Macroinvertebrates have
        a strong standing in stream health assessment (Bonada et al.
        2006, Birk et al. 2012), and TN can be related to catchment
        N loading, so we suggest TN is more suitable for objective
        setting than DIN.
        
        We found strong negative relationships between TN
        and %EPT taxa or the MCI, which is a metric calculated
        from tolerance values. These results suggest that N is a
        pervasive stressor for macroinvertebrate communities. Impact
        initiation thresholds of these 2 metrics were ~0.2 mg
        TN/L. A higher impact initiation threshold for EPT richness,
        at ~0.4 mg TN/L, probably reflects that some EPT
        taxa are tolerant to or even benefit from initial nutrient
        enrichment (Wagenhoff et al. 2012).
        
        Therefore, a small increase in the N concentration
        above background levels seems to be associated with
        structural change to different ecosystemcomponents, an observation
        also made by other investigators (Smith and Tran
        2010).
        
        The impact cessation threshold of
        0.5 mg TN/L is well below the 1 mg NO3-N/L objective
        set in New Zealand’s National Objectives Framework
        (MfE 2014) to protect the most sensitive aquatic species
        (including macroinvertebrates) from NO3 toxicity.
  - - - At low concentrations the presence of nutrient
        may act to increase food sources, especially algae, causing some
        taxa to thrive and thus act as positive indicators
      - These latter Site Types are more
        challenging to analyse because of the more complex nature of the pollutant cocktail, and the approach suggested is likely to be less useful (ie more useful at less polluted sites, not so much at more polluted sites
- - - - The physiological effects can be lethal in case of high toxic concentrations of N compounds, but mostly result in sub-lethal effects associated with reduced feeding activity, fecundity and eventually survival, which decreases population sizes of
        aquatic animals (Camargo and Alonso, 2006).