Macroinvertebrate Community Index (MCI) is an

index Index (or its plural form indices) may refer to: Arts, entertainment, and media Fictional entities * Index (''A Certain Magical Index''), a character in the light novel series ''A Certain Magical Index'' * The Index, an item on a Halo megastru ...

used in

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

to measure the

water quality Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through tr ...

of fresh water streams. The presence or lack of

macroinvertebrates Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate s ...

such as insects, worms and snails in a river or stream can give a

biological indicator A bioindicator is any species (an indicator species) or group of species whose function, population, or status can reveal the qualitative status of the environment. The most common indicator species are animals. For example, copepods and other sma ...

on the health of that waterway. The MCI assigns a number to each

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of macroinvertebrate based on the sensitivity of that species to

pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...

. The index then calculates an average score. A higher score on the MCI generally indicates a more healthy stream. The MCI (Macroinvertebrate Community Index) relies on an allocation of scores to freshwater macroinvertebrates based on their pollution tolerances. Freshwater macroinvertebrates found in pristine conditions would score higher than those found in polluted areas.Stark, J. D. (1993) Performance of the Macroinvertebrate Community Index: Effects of sampling method, sample replication, water depth, current velocity, and substratum on index values. New Zealand Journal of Marine and Freshwater Research 27:4, 463-478. MCI values can be calculated using macroinvertebrate presence-absence data using this equation: MCI = site score)/(# of scoring taxa)20 Previous

assessments have relied on both chemical and habitat analysis, however, these methods have been proven to be insufficient due to pollution from nonpoint sources.Bennett, H. H., M. W. Mullen, P. M. Stewart, J. A. Sawyer, and E. C. W. (2004) Development of an Invertebrate Community Index for an Alabama Coastal Plain Watershed. Journal of the American Water Resources Association, 40:1, 43-51 Species living in an aquatic environment may be the best natural indicator of environmental quality and reveal the effects of any habitat alteration or pollution, and have proved to respond to a wide range of stressors such as

sedimentation Sedimentation is the deposition of sediments. It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to the ...

urbanization Urbanization (or urbanisation) refers to the population shift from rural to urban areas, the corresponding decrease in the proportion of people living in rural areas, and the ways in which societies adapt to this change. It is predominantly t ...

agricultural Agriculture or farming is the practice of cultivating Plant, plants and livestock. Agriculture was the key development in the rise of Sedentism, sedentary human civilization, whereby farming of Domestication, domesticated species created food ...

practices and forest harvesting effects.Collier, KJ. (2014) Wood decay rates and macroinvertebrate community structure along contrasting human pressure gradients (Waikato, New Zealand), New Zealand Journal of Marine and Freshwater Research, 48:1, 97-111 Any changes that may occur in macroinvertebrate communities that lead to a reduction in diversity increase the dominance of pollution-tolerant invertebrates, such as

oligochaetes Oligochaeta () is a subclass of animals in the phylum Annelida, which is made up of many types of aquatic and terrestrial worms, including all of the various earthworms. Specifically, oligochaetes comprise the terrestrial megadrile earthworms ...

and

chironomids The Chironomidae (informally known as chironomids, nonbiting midges, or lake flies) comprise a family of nematoceran flies with a global distribution. They are closely related to the Ceratopogonidae, Simuliidae, and Thaumaleidae. Many species ...

.Hall, M. J., G. P. Closs and R. H. Riley. (2001) Relationships between land use and stream invertebrate community structure in a South Island, New Zealand, coastal stream catchment. New Zealand Journal of Marine and Freshwater Research, 35:3, 591-603 Thus, a lack of species diversity and low

biotic index A biotic index is a scale for showing the quality of an environment by indicating the types and abundances of organisms present in a representative sample of the environment. It is often used to assess the quality of water in marine and freshwater ...

scores of inhabitant macroinvertebrates may be an indicator of poor water quality.Collins, C. L., M. W. Mullen, P. M. Stewart, and E. C. Webber. (2008) Validation of an Invertebrate Community Index for Urban Streams for an Alabama Coastal Plains Watershed. Journal of The American Water Resources Association, 44(3), 663-669 The risk of water quality degradation is the greatest in low-elevation areas, where high intensity agriculture and urban development are the dominant land uses.Larned, S. T., T. Snelder, M. J. Unwin, and G.B. McBride. (2016) Water quality in New Zealand rivers: current state and trends. New Zealand Journal of Marine and Freshwater Research, 50:3, 389-417 Macroinvertebrate communities are the preferred indicators of

aquatic ecosystem An aquatic ecosystem is an ecosystem formed by surrounding a body of water, in contrast to land-based terrestrial ecosystems. Aquatic ecosystems contain communities of organisms that are dependent on each other and on their environment. The tw ...

health because they are very easy to both collect and identify, and have short life spans, thus responding very quickly to changes in their environment. The MCI methods of utilizing macroinvertebrate communities to assess the overall health of an aquatic environment continues to be the most reliable, applicable, and widely acclaimed method around the world.Olomukoro, J. O. and A. Dirisu. (2014) Macroinvertebrate Community and Pollution Tolerance Index in Edion and Omodo Rivers in Derived Savannah Wetlands in Southern Nigeria. Jordan Journal of Biological Sciences, 7:1, 19-24. Variations on the MCI In addition to the MCI indexed defined above, there are also two other variations of the MCI. The QMCI (Quantitative Macroinvertebrate Community Index) and the SQMCI (Semi-Quantitative Macroinvertebrate Community Index). Both MCI and QMCI are widely used in countries like New Zealand. The combination of widespread use and good performance of the MCI and the QMCI in detecting water quality in aquatic ecosystems has sparked interest in further refinement of the methods in New Zealand.Stark, J. D. (1998) SQMCI: A biotic index for freshwater macroinvertebrate coded-abundance data. New Zealand Journal of Marine and Freshwater Research, 32:1, 55-66. The QMCI, just like the MCI, was initially designed to evaluate the organic enrichment in aquatic ecosystems. The third index, the SQMCI, was created to reduce sampling and processing efforts required for the QMCI.Wright-Stow, A. E. and Winterbourn, M. J. (2003) How well do New Zealand's stream-monitoring indicators, the macroinvertebrate community index and its quantitative variant, correspond? New Zealand Journal of Marine and Freshwater Research, 37:2, 461-470. The SQMCI will respond in a similar matter to the QMCI in community dominance, however, will require fewer samples to achieve the same precision. The SQMCI gives a comparative appraisal to the QMCI with under 40% of the

exertion Exertion is the physical or perceived use of energy.Newton's Third Law, Elert, Glenn. “Forces.” ''Viscosity – The Physics Hypertextbook'', physics.info/newton-first/. Exertion traditionally connotes a strenuous or costly ''effort'', resulting ...

, in circumstances that macroinvertebrate densities are not required. This diminishes expenses and also enhances the logical solidness of biomonitoring projects. Both the QMCI and SQMCI are similar to the MCI in the way that they are graded on a 1 (extremely tolerant) to 10 (highly intolerant) scale. However, they differ in the way that MCI is calculated using presence-absence data whereas QMCI uses quantitative or percentage data. Having a qualitative, quantitative, and semi-quantitative version of the same index has raised some questions as to if this is a good thing or not. All three indexes have the same purpose, which is to measure the quality of an aquatic ecosystem, however, there are no clear recommendations about when each one is most appropriate to be used. In a study conducted on 88 rivers, Scarsbrook et al. (2000) concluded MCI is more useful than the QMCI for recognizing changes in stream water quality over time. Having three forms of a similar index may prompt to various conclusions and also opens the route for specific utilization of either file to give bias to a specific position or position taken by a specialist. In August 2019, the Ministry for the Environment released a draft National Policy Statement for Freshwater Management, and a report from Scientific and Technical Advisory Group that recommended including three different measures, MCI, QMCI and Average Score Per Metric (ASPM). QMCI values can be calculated using: QMCI = Σ_(i=1)^(i=s)▒(n_i*a_i)/N SQMCI values can be calculated similar to QMCI except that coded abundances are substituted for actual counts. Example: SQMCI = Σ_(i=1)^(i=s)▒(n_i*a_i)/N Factors Influencing MCI There are several factors which can affect the data acquisition of MCI when assessing the water quality of an aquatic ecosystem. Hard-bottom and Soft-bottom channels can often yield different results and many researchers will use two different versions of the MCI. For example, in a study by Stark & Mallard (2007) they discuss that hard and soft bottom channels have separate versions of the MCI and the two versions can not be combined into one data set because of the differences in

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

and tolerance values.

Spatial variability Spatial variability occurs when a quantity that is measured at different spatial locations exhibits values that differ across the locations. Spatial variability can be assessed using spatial descriptive statistics such as the range. Let us supp ...

is also of interest in terms of affecting the data acquired through MCI. Sites which are progressively down stream often tend to yield a lower MCI value. There may also be confounding influences between riffles, runs, or pools with a single stream reach.Stark, J. D. and N. Phillips. (2009) Seasonal variability in the Macroinvertebrate Community Index: Are seasonal correction factors required? New Zealand Journal of Marine and Freshwater Research, 43:4, 867-882 Depth and velocity have also been raised as a concern with regards to effecting results, however Stark (1993) investigated the influences of the sampling method, water depth, current velocity and

substratum In linguistics, a stratum (Latin for "layer") or strate is a language that influences or is influenced by another through contact. A substratum or substrate is a language that has lower power or prestige than another, while a superstratum or sup ...

on the results and found that both MCI and QMCI are independent of depth, velocity, and substratum from macroinvertebrate samples collected from stony riffles. This finding is an advantage for the assessment of water pollution. There have been several studies conducted on seasonal variability, which has been considered the main influential factor on the assessment of water quality. It has been concluded that all models should test data that has been collected in the season as the reference data, which is being used. There have been several other factors such as water temperature, invertebrate life histories and dissolved oxygen levels that have all been explained as causes of seasonal variability. Warmer seasons have biotic indices that are indicative of poorer stream health. Warmer seasons such as summer, would have increased temperatures therefore increasing water temperature and decreasing the amount of dissolved oxygen in the water making the environment less ideal to aquatic macroinvertebrates. In return, this effects the density of macroinvertebrate population and changes the results of the indices.

References

External links

A user guide for Macroinvertebrate Community IndexDiscussion on Radio New Zealand about MCI values of Hawkes Bay streams and riversList of indicator species used to calculate the MCI number
{{DEFAULTSORT:Macroinvertebrate Community Index Environmental science Water Water management Water pollution Water in New Zealand