Do abundance and percentage of dipteran larvae and Oligochaeta indicate low water quality in streams and lake littoral?

Type	Water properties	Catchment (km²) area	Alkalinity (mgl⁻¹ HCO₃⁻)	Cond(μS cm⁻¹)	Salinity(mgl⁻¹ Cl⁻)	Strat	n
Streams
I A	Dark water (> 25)	10−100					44
I B	Light water (< 25)	10−100					70
II A	Dark water (> 25)	100−1000					31
II B	Light water (< 25)	100−1000					75
III A	Dark water (> 25)	1000−10 000					1
III B	Light water (< 25)	1000−10 000					19
IV		> 10 000					2
Lakes
I	Calcareous		> 240	> 400	< 25	no	1
II	Medium water hardness		80–240	165–400	< 25	no	49
III	Medium water hardness		80–240	165–400	< 25	yes	13
IV	Soft water, dark (≥ 4)		< 80	< 165	< 25	no	9
V	Soft water, light (≤ 4)		< 80	< 165	< 25	no	19
VIII	Former lagoons (distance from the sea < 5 km)				> 25	no	12

[i] Water color: streams − COD_Mn as mg l⁻¹ O (90% of values); lakes – absorption coefficient per m at 400 nm (in IV and V). Cond − conductivity, Strat – stratification

Table 2

Frequency of different dipteran groups and oligochaetes in streams and lakes

	Streams		Lakes
	n	%	n	%
Chironomidae	241	99.6	103	100
Oligochaeta	210	86.8	86	83.5
Ceratopogonidae	108	44.6	63	61.2
Simuliidae	161	66.5	0	0
Athericidae: Atherix	92	38.0	0	0
Chaoboridae: Chaoborus	3	1.2	14	13.6
Culicidae	8	3.3	3	2.9
Cylindrotomidae: Phalacrocera replicata	1	0.4	2	1.9
Dixidae	6	2.5	6	5.8
Dolichopodidae	4	1.7	1	1.0
Limoniidae: Antocha	22	9.1	0	0
Limoniidae: Eloeophila	97	40.1	1	1.0
Limoniidae: Gnophomyia	1	0.4	1	1.0
Muscidae: Limnophora	17	7.0	0	0
Pediciidae: Dicranota	105	43.4	1	1.0
Psychodidae: Pericoma	21	8.7	0	0
Ptychopteridae: Ptychoptera	9	3.7	1	1.0
Sciomyzidae	1	0.4	0	0
Stratiomyiidae	3	1.2	1	1.0
Syrphidae	0	0	1	1.0
Tabanidae: Chrysops	41	16.9	6	5.8
Tipulidae	29	12.0	2	1.9
Diptera indet.	106	43.8	9	8.7

Table 3

Mean abundance (individuals m⁻² ± SE) and contribution of the most abundant dipteran groups and oligochaetes in streams and lakes

	Streams		Lakes
	mean ± SE	%	mean ± SE	%
Chironomidae	142 ± 35	24.2	93 ± 11	32.6
Oligochaeta	21 ± 3	3.6	23 ± 5	8.1
Ceratopogonidae	1.7 ± 0.5	< 0.1	5.3 ± 1.0	1.9
Simuliidae	68 ± 30	11.6	0	0
Atherix	4.1 ± 1.0	0.7	0	0
Eloeophila	1.3 ± 0.2	< 0.1	< 0.1	< 0.1
Dicranota	2.9 ± 0.4	< 0.1	< 0.1	< 0.1

Table 4

Significant differences between the abiotic characteristics (> and <, columns 2–4); positive (+) and negative (–) directions of significant relationships between biotic metrics and abiotic factors (columns 5–8)

Variable	S vs L	S: dark water vs light water	L: hard water vs soft water	S: DistS	All: pH	All: O₂	All: Cond
1	2	3	4	5	6	7	8
Chir		<*
Chir%	<***
Olig		>*		+***	+ **	+*
Olig%				+***	+**		–**
Cer	<***
Cer%	<***
Sim	---		---	–**
Sim%	---		---
DiptR	>***		<*	–*		+**

[i] ^*** – p-value < 0.0001, ^** – p-value < 0.01, ^* – p-value < 0.05. S – streams, L– lakes, All – streams and lakes. Chir − abundance of chironomids, Chir% − percentage of chironomids, Olig − abundance of oligochaetes, Olig% – percentage of oligochaetes, Cer – abundance of ceratopogonids, Cer% – percentage of ceratopogonids, Sim – abundance of simuliids, Sim% – percentage of simuliids, DiptR – richness of dipteran families. DistS – distance from a stream source, O₂ – water oxygen content, Cond – water conductivity

Table 5

Significant relationships with model parameter estimates between biotic metrics and water quality factors (where relevant)

	Comparison	Streams	Lakes
EQRMMQ	Chir		−0.5**
	Olig	0.8***	−0.7*
	Cer		−2.2***
	Sim	2.5***
	Chir%	-0.2**	−0.5***
	Olig%		−0.3**
	Cer%		−0.1*
	DiptR	3.8***
MESH	Olig	0.18*	0.6**
	Cer	−1.1*
	Sim	2.3*
	Chir%	−0.1*
	Cer%	−0.04***
	DiptR	3.8***
QWat	Olig		−1.2**
QWat	Olig%		−0.1**
QFish	Olig	0.2*
QFish	Olig%	0.03**
QPhybe	DiptR	0.4*
	Olig		−0.3**
	Olig%		−0.06**
EQRT	Olig	0.2*	−0.5*
	Cer	1.4***
	Chir%		−0.4***
	Cer%	0.03**	−0.1**
	DiptR	1.6***
EQREPT	Chir	6.1***	**
	Olig	0.5***	−0.4**
	Chir%		−0.1*
	Olig%		−0.1*
	Cer%		−0.05**
	DiptR	1.7***
EQRH’	Chir	−0.9***	−0.7***
	Olig	1.3***
	Sim Chir%	1.5 −0.3*	−0.1*
	Olig%	0.07**
	DiptR	1.6**
EQRASPT	Olig	−0.8*	−1.8**
	Olig%		−0.7**
	DiptR	4.5***

[i] ^*** – p-value < 0.001, ^** – p-value < 0.01, ^* – p-value < 0.05. Metrics: Chir – abundance of chironomids, Chir% − percentage of chironomids, Olig – abundance of oligochaetes, Olig% – percentage of oligochaetes, Cer – abundance of ceratopogonids, Cer% – percentage of ceratopogonids, Sim – abundance of simuliids, percentage of simuliids Sim%, DiptR – richness of dipteran families. Quality factors: EQR – ecological quality ratio, MMQ – macroinvertebrate-based multimetric quality, T – total taxon richness, H’ – Shannon diversity index, ASPT – Average Score Per Taxon, EPT – Ephemeroptera, Plecoptera and Trichoptera taxon richness; MESH – hydromorphological score, QWat – water quality, QFish – fish quality, QPhybe – phytobenthos quality, QPhypl – phytoplankton quality