The AMBI is one of several international marine biotic indices that assesses estuarine health based on the types and numbers of macrofauna and their known tolerances to environmental stress (see the “Dominant species” tab). AMBI scores range from 0-7 and are based on the proportion of taxa falling into one of five eco-groups (EG) that reflect sensitivity to pollution (e.g., organic enrichment, mud deposition), ranging from relatively sensitive (EG-I) to relatively resilient (EG-V). Lower AMBI values indicate better ecological conditions.

AMBI scores over time have indicated that the muddier site in Catlins Lake (Site B) has more hardy species in EG-IV, while EG- I to III were predominant at Site A in the lower estuary. Drag the slider at the top of the AMBI map to change surveys.

Over time, the number of different species (richness) and total number of individuals (abundance) have increased at Site A. At Site B species richness has remained steady, but abundance increased in Dec-2023, owing to a high number of the disturbance tolerant species Paracorophium excavatum (see photo).

The composition pattern recorded at Site B is often associated with changes in sediment mud content and enrichment levels that can create conditions better suited to a greater number of smaller more ‘hardy’ species. Refer to the AMBI tab or overview map for site locations.

The table below provides a description of the most dominant macrofauna species at Catlins Estuary monitoring sites. The dominant species represent five main organism groups: bivalves (shellfish), polychaete and oligochaete worms, shrimp-like amphipods and anemones.

EG denotes the species’ eco-group, ranging from relative sensitivity (I) to hardiness (V). The charts on the right show how species’ abundances (average abundances in sediment cores collected at each site) have changed across surveys; refer to the AMBI tab or overview map for site locations.

Name	EG	Description	Image1	Site abundance
Bivalve Legrandina turneri	NA	A small bivalve that appears to be an endemic southern New Zealand species. Diet and ecogroup unknown.		place holder for interactive chart
Bivalve Lasaea parengaensis	II	Small and little-known bivalve. Probably a prey item in the diet of birds and fish.		place holder for interactive chart
Amphipod Paracorophium excavatum	IV	Corophioid amphipod that is an opportunistic tube-dweller, tolerant of muddy and low salinity conditions.		place holder for interactive chart
Polychaete Prionospio aucklandica	III	Deposit-feeding spionid worm, common in harbours and estuaries. P. aucklandica is associated mainly with muddy sands, but occurs across a range of mud contents and is rated as EG-III. Considered tolerant to organic enrichment.		place holder for interactive chart
Polychaete Boccardia syrtis	II	A small surface deposit-feeding spionid. Found in a wide range of sand/mud habitats. Lives in flexible tubes constructed of fine sediment grains, and can form dense mats on the sediment surface. Sensitive to organic enrichment.		place holder for interactive chart
Anthozoa Edwardsia sp.	II	A tiny elongate anemone adapted for burrowing; colour very variable, usually 16 tentacles but up to 24, pale buff or orange in colour. Prefers sandy sediments with low-moderate mud and is usually intolerant of anoxic conditions.		place holder for interactive chart
Amphipod Waitangi brevirostris	II	A mobile predator and scavenger that occurs across the middle (and sometimes lower) part of the intertidal range on exposed sandy beaches and is likely to play an important role in sediment reworking.		place holder for interactive chart
Polychaete Scolecolepides benhami	IV	A spionid, surface deposit feeder. It is rarely absent in sandy/mud estuaries, often occurring in a dense zone high on the shore, although large adults tend to occur further down towards low water mark.		place holder for interactive chart
Bivalve Arthritica sp. 5	III	A small sedentary deposit feeding bivalve that lives buried in the mud. Tolerant of muddy sediments and moderate levels of organic enrichment.		place holder for interactive chart
Oligochaete Oligochaeta	V	Segmented worms in the same group as earthworms. Deposit feeders that are generally considered pollution or disturbance tolerant.		place holder for interactive chart
Polychaete Capitella cf. capitata	V	Subsurface deposit feeder, occurs down to about 10 cm sediment depth. Common indicator of organic enrichment or other forms of disturbance. Is a dominant inhabitant of sediments polluted heavily with organic matter.		place holder for interactive chart
Amphipod Paracalliope novizealandiae	I	Small and little-known bivalve. Probably a prey item in the diet of birds and fish.		place holder for interactive chart

1. Images from NIWA; pink colour is a stain that is used to help with species identification.