Crustacean zooplankton dynamics in a natural riverine lake, Upper Mississippi River

Figures & data

Figure 1. Map of Upper Mississippi River Navigation Pool 4, including Lake Pepin and fixed site M766.0I.

Table 1. Percent occurrence (percentage of samples where taxa occurred) of crustacean zooplankton collected in Lake Pepin. Fixed site data were collected at site M766.0I from 1996 through 2012. Stratified random sampling (SRS) data were collected during summer (late-July to early-August) and fall (mid-October) SRS episodes from 1995 through 2012.

	Percent occurrence
	Fixed site						SRS episodes
	May	Jun	Jul	Aug	Sep	Oct	Summer	Fall
Cladocera
Alona sp.	2.9	5.3	0	0	0	0	0.2	0.7
Bosmina longirostris	85.3	76.3	32.4	65.6	80.0	100	48.4	91.4
Ceriodaphnia sp.	20.6	23.7	2.9	15.6	0	11.8	16.5	16.2
Chydorus sphaericus	88.2	60.5	29.4	25.0	28.0	35.3	14.8	41.8
Diaphanosoma birgei	0	18.4	61.8	93.4	96.0	35.3	87.4	28.9
Daphnia ambigua	5.9	0	2.9	0	0	0	0	0
Daphnia galeata mendotae	64.7	84.2	79.4	68.8	72.0	76.5	56.3	59.4
Daphnia lumholtzi^a	0	0	0	18.5	33.3	16.7	0.2	27.6
Daphnia parvula	32.4	29.0	5.9	9.4	20.0	35.3	6.3	23.7
Daphnia pulicaria	58.8	50.0	11.8	21.9	8.0	11.8	12.6	15.3
Daphnia retrocurva	32.4	97.4	97.0	96.9	96.0	70.6	86.2	78.8
Eubosmina coregoni	5.9	13.2	5.9	12.5	8.0	11.8	5.3	12.0
Eurycercus lamellatus	0	7.9	0	0	0	0	0.2	0.7
Latona setifera	0	0	0	0	0	0	0.2	0.2
Leptodora kindtii	5.9	34.2	32.4	31.2	32.0	0	28.2	8.1
Macrothricidae	8.8	10.5	2.9	0	0	0	4.5	1.8
Moina sp.	0	2.6	0	12.5	4.0	5.9	18.3	5.6
Pleuroxus sp.	0	0	0	0	0	0	0	0.2
Scapholeberis sp.	0	0	0	0	0	0	0.6	0
Sida crystallina	0	2.6	0	3.1	0	0	1.8	0.2
Simocephalus sp.	0	5.3	0	0	0	5.9	0	0.4
Copepoda
Calanoid	41.2	28.9	47.0	68.8	80.0	94.1	38.4	84.4
Copepodite	97.0	92.1	100	100	100	100	97.8	96.4
Cyclopoid	100	97.4	100	100	100	100	99.2	99.1
Harpacticoid	0	0	0	0	0	0	0	0.2
Nauplii	97.0	94.7	100	96.9	100	100	99.0	99.1

^a Daphnia lumholtzi was first recorded in 1999. Frequency calculated from 1999 through 2012.

Table 2. Mean density, biomass and maximum abundance of crustacean zooplankton collected in Lake Pepin. Fixed site data were collected at site M766.0I from 1996 through 2012. Stratified random sampling (SRS) data were collected during summer (late-July to early-August) and fall (mid-October) SRS episodes from 1995 through 2012. Numbers in parentheses show standard error of the mean.

	Density (individual l^−1)				Biomass (μg l^−1)
Zooplankton	Fixed	Summer	Fall	Max.	Fixed	Sum	Fall	Max.
Cladocera
Alona sp.	<0.1(<0.1)	<0.1(<0.1)	<0.1(<0.1)	0.6^d	<0.1(<0.1)	<0.1(<0.1)	<0.1(<0.1)	0.2^d
Bosmina longirostris	2.0 (0.4)	0.2(<0.1)	1.7 (0.2)	82.1^d	3.7 (0.8)	0.3(<0.1)	2.6 (0.3)	98.3^d
Ceriodaphnia sp.	<0.1(<0.1)	<0.1(<0.1)	<0.1	1.3^b	0.1(<0.1)	<0.1(<0.1)	<0.1(<0.1)	1.4^b
Chydorus sphaericus	0.4 (0.1)	0.1(<0.1)	0.1(<0.1)	15.8^c	0.5 (0.1)	0.1(<0.1)	0.1(<0.1)	16.2^b
Diaphanosoma birgei	1.1 (0.2)	1.4 (0.1)	0.1(<0.1)	23.5^c	3.5 (0.5)	4.1 (0.3)	0.5 (0.1)	55.9^c
Daphnia ambigua	<0.1(<0.1)	0	0	0.6^b	<0.1(<0.1)	0	0	1.3^b
Daphnia galeata mendotae	2.1 (0.3)	0.4(<0.1)	0.7 (0.1)	36.2^c	22.4 (4.3)	5.4 (1.0)	5.1 (0.7)	439.5^b
Daphnia lumholtzi^a	<0.1(<0.1)	<0.1(<0.1)	<0.1(<0.1)	3.9^b	0.4 (0.2)	<0.1(<0.1)	0.5 (0.1)	25.4^d
Daphnia parvula	0.1(<0.1)	<0.1(<0.1)	<0.1(<0.1)	5.0^b	0.9 (0.4)	0.1(<0.1)	0.2(<0.1)	74.5^b
Daphnia pulicaria	0.3(<0.1)	<0.1(<0.1)	<0.1(<0.1)	6.3^b	2.9 (0.7)	0.2(<0.1)	0.2(<0.1)	86.7^b
Daphnia retrocurva	6.2 (0.8)	6.0 (1.0)	0.9(<0.1)	430.9^c	23.7 (3.6)	23.7 (3.4)	2.6 (0.2)	1080.8^c
Eubosmina coregoni	0.1(<0.1)	<0.1(<0.1)	0.1(<0.1)	5.4^d	0.3 (0.1)	0.1 (0.0)	0.3 (0.1)	16.4^d
Eurycercus lamellatus	<0.1(<0.1)	<0.1(<0.1)	<0.1(<0.1)	2.2^c	<0.1(<0.1)	<0.1(<0.1)	<0.1(<0.1)	4.2^c
Latona setifera	0	<0.1(<0.1)	<0.1(<0.1)	<0.1^d	0	<0.1(<0.1)	<0.1(<0.1)	0.4^d
Leptodora kindtii	<0.1(<0.1)	0.1(<0.1)	<0.1(<0.1)	9.8^c	0.9 (0.2)	0.7 (0.1)	0.1(<0.1)	45.2^c
Macrothricidae	<0.1(<0.1)	<0.1(<0.1)	<0.1(<0.1)	1.5^c	<0.1(<0.1)	<0.1(<0.1)	<0.1(<0.1)	2.1^c
Moina sp.	<0.1(<0.1)	<0.1(<0.1)	<0.1(<0.1)	3.9^c	<0.1(<0.1)	0.1(<0.1)	<0.1(<0.1)	5.3^c
Pleuroxus sp.	0	0	<0.1(<0.1)	<0.1^d	0	0	<0.1(<0.1)	<0.1^d
Scapholeberis sp.	0	<0.1(<0.1)	0	0.1^c	0	<0.1(<0.1)	0	<0.1^c
Sida crystallina	<0.1(<0.1)	<0.1(<0.1)	<0.1(<0.1)	3.6^c	<0.1(<0.1)	<0.1(<0.1)	<0.1(<0.1)	18.0^c
Simocephalus sp.	<0.1(<0.1)	0	<0.1(<0.1)	0.5^b	<0.1(<0.1)	0	<0.1(<0.1)	4.8^b
Copepoda
Calanoid	0.6 (0.1)	0.2(<0.1)	0.9(<0.1)	19.9^d	4.8 (0.2)	1.4 (0.2)	8.8 (1.0)	225.0^d
Copepodite	3.3 (0.3)	3.2 (0.2)	1.3(<0.1)	42.4^c	4.0 (0.4)	3.9 (0.2)	1.6 (0.1)	46.3^c
Cyclopoid	8.3 (0.6)	6.6 (0.4)	4.0 (0.3)	59.0^b	39.4 (3.2)	27.7 (1.6)	16.1 (1.2)	281.7^b
Harpacticoid	0	0	<0.1(<0.1)	0.2^d	0	0	<0.1(<0.1)	1.3^d
Nauplii	9.6 (0.8)	9.5 (0.6)	4.0 (0.3)	164.5^c	1.7 (0.1)	1.6 (0.1)	0.7(<0.1)	27.2^c
Total	34.4	28.0	13.9		109.2	69.5	39.5

^a Abundance for Daphnia lumholtzi was calculated from 1999 through 2012 as it was first discovered in 1999. ^bMaximum abundance occurred at the fixed site, ^cduring summer SRS or ^d fall SRS.

Table 3. Percent occurrence (percentage of samples where taxa occurred) of copepod zooplankton collected at site M766.0I in Lake Pepin (50 randomly chosen samples were analyzed from 1996 through 2012).

	Percent occurrence
Calanoids
Skistodiaptomus oregonensis	46.0
Leptodiaptomus siciloides	12.0
Skistodiaptomus pallidus	4.0
Cyclopoids
Acanthocyclops vernalis	90.0
Mesocyclops edax	42.0
Diacyclops bicuspidatus thomasi	20.0
Tropocyclops prasinus mexicanus	10.0
Eucyclops prionophorus	4.0
Macrocyclops albidus	2.0
Ectocyclops phaleratus	4.0

Figure 2. Mean monthly abundance of cladocerans and copepods in Lake Pepin from 1996 through 2012 at fixed site M766.0I. Nauplii and copepodites are not included.

Figure 3. Non-metric multidimensional scaling (NMDS) ordination of Lake Pepin crustacean zooplankton sampled during summer stratified random sampling (SRS) episodes from 1995 through 2012. For graphical presentation, abundance was averaged over sites by (a) year and (b) 3.2 km reach (numbers are river miles) and overlaid with average water residence time.

Figure 4. NMDS ordination of Lake Pepin crustacean zooplankton sampled during fall SRS episodes from 1995 through 2012. For graphical presentation, abundance was averaged over sites by (a) year and (b) reach and overlaid with average water residence time.

Figure 5. Mean biomass of crustacean zooplankton in Lake Pepin from 1995 through 2012 by 3.2 km reach during (a) summer and (b) fall SRS episodes.

Figure 6. Mean biomass of crustacean zooplankton in Lake Pepin from 1995 through 2012 during (a) summer and (b) fall SRS episodes.

Table 4. Rank correlation coefficients (ρ) between zooplankton among-sample patterns of assemblage and associated environmental variables. Data collected during summer and fall SRS episodes (1995--2012).

Season	ρ	No.	Variables
Summer	0.317	1	WRT
	0.298	2	WRT, SS
	0.279	2	WRT, PCTOM
	0.279	3	WRT, SS, PCTOM
	0.272	4	WRT, SS, PCTOM, TEMP
	0.271	3	WRT, SS, TEMP
Fall	0.299	1	WRT,
	0.257	2	WRT, VSS
	0.236	2	WRT, SS
	0.227	3	WRT, VSS, TEMP
	0.225	2	WRT, TEMP
	0.225	2	WRT, CHL

Note: Variables are defined as water residence time (WRT) suspended solids (SS), percent organic matter (PCTOM), water temperature (TEMP), volatile suspended solids (VSS) and chlorophyll a (CHL).

P < 0.001.

Figure 7. Spearman's rank correlation between water residence time and cladocerans during (a) summer and (b) fall SRS episodes, copepods during (c) summer and (d) fall SRS episodes and chlorophyll a during (e) summer and (f) fall episodes.

Figure 8. Mean total suspended solids during (a) summer and (b) fall SRS episodes and percent organic matter during (c) summer and (d) fall SRS episodes. Sites sampled in Lake Pepin from 1995 through 2012 and averaged by 3.2 km reach (numbers are river miles).