Northeastern Naturalist Vol. 26, No. 2
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019
343
2019 NORTHEASTERN NATURALIST 26(2):343–361
Rediscovery of the Freshwater Brown Alga Heribaudiella in
Connecticut After 100 Years
John D. Wehr1,*, Sarah E. Steirer1, and Robin S. Sleith2
Abstract - Heribaudiella fluviatilis is a freshwater species in the predominantly marine
class of brown algae (Phaeophyceae). The first reported North American population was
collected in 1898 from Island Brook, CT. Here we confirm that the species was once present
in Island Brook but has been extirpated from that location. Our 2016 survey rediscovered
Heribaudiella in the New England flora, in 6 streams in western Connecticut ~70 km inland
from marine water. Ecological data indicate these streams are deeper and have large-grained
sediments, but lower specific conductance, dissolved NO3
-, and inorganic P as soluble
reactive phosphorous (SRP) than nearby streams lacking this alga. We ran a multivariate,
boosted regression tree (BRT) analysis, which confirmed that the niche of Heribaudiella in
Connecticut is limited to minimally disturbed streams with greater pH, a high percentage of
streambed boulders, and lower concentrations of dissolved NO 3
- and SRP.
Introduction
Brown algae, comprising the class Phaeophyceae, form a group of roughly 2000
species, nearly all of which occupy marine waters. This group of golden-brown,
photosynthetic organisms vary in size and morphology from microscopic filaments
to giant kelps many meters in length, with complex reproductive structures and life
cycles (Graham et al. 2016). A very small number of brown algal species—perhaps
6 or 7 in total—occur in freshwater environments (Wehr 2015). Most of these taxa
are known from very few localities worldwide, leading some to suggest their global
rarity, as compared with most species in the freshwater algal flora (Wehr 2015).
Researchers have observed that some populations of freshwater phaeophytes occur
near coastal waters and have suggested that these representatives may have invaded
freshwater habitats relatively recently (Israelsson 1938, Waern 1952, Wilce 1966).
Thus far, molecular data (rbcL chloroplast gene) have indicated that most of the
known freshwater species are members of separate clades within the class (Mc-
Cauley and Wehr 2007), although their tolerance of saline water has not been tested
(Wehr 2015).
Of those few freshwater species, Heribaudiella fluviatilis (Aresch.) Sved. is the
most widely reported, with roughly 30 records from North America, nearly all of
which are in western states and provinces, with 1 putative population from Tennessee
(Johansen et al. 2007, Wehr 2015, Wehr and Stein 1983). The alga forms
conspicuous brown crusts on rocks and can become a major part of the benthic
1Louis Calder Center–Biological Field Station and Department of Biological Sciences,
Fordham University, Armonk, NY 10504. 2Lewis B. and Dorothy Cullman Program for
Molecular Systematics, The New York Botanical Garden, Bronx, NY 10458. *Corresponding
author - wehr@fordham.edu.
Manuscript Editor: Hunter Carrick
Northeastern Naturalist
344
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019 Vol. 26, No. 2
algal community in streams (Holmes and Whitton 1975, Wehr and Stein 1985).
H. fluviatilis typically colonizes rocky, clear streams with high current velocity and
relatively low concentrations of dissolved phosphorus (Holmes and Whitton 1975,
Schneider and Lindstrøm 2011, Wehr 2015, Wehr and Perrone 2003). It has been
reported from rivers and streams in subarctic to temperate locations in Europe, Japan,
China, and Russia, but thus far has not been observed in subtropical or tropical
locations, or in any streams in the Southern Hemisphere (W ehr 2016).
The species was first described as Lithoderma fluviatile by Areschoug (1875;
the basionym), but later transferred to a new genus, Heribaudiella, by Svedelius
(1930), as Lithoderma is a marine genus with different reproductive structures. Notably,
the very first collection of Heribaudiella from North America (as Lithoderma
fluviatile Aresch.) was by Isaac Holden in 1898 from Island Brook in Connecticut,
and was documented in the exsiccatae of algae Phycotheca Boreali-Americana
(Collins et al. 1898). Those specimens are deposited in several major herbaria in the
US. That single record stood for decades, until Smith (1950) in Freshwater Algae
of the United States, cast doubt on the identity of Holden’s 1898 collection from
Island Brook, due to its proximity to the high tide, and suggested it was likely a
different marine species. Later reports from British Columbia and elsewhere (e.g.,
Pueschel and Stein 1983, Wehr and Stein 1985) resurrected the species as part of
the North American flora, but the identity of the Connecticut population remained
a mystery. Given the apparent rarity of Heribaudiella globally and especially in the
eastern US, we endeavored to determine whether Holden’s collections were properly
identified and if the population still existed in its original location, examine
streams more widely for its presence within Connecticut, and if present, compare its
morphology and ecological niche, based on chemical and geophysical properties,
with that known for this species in other regions.
Field-site Description
We conducted the field portion of this study in mid- and late summer 2016
in western Connecticut, in river basins at varying distances from Island Brook in
Bridgeport, CT, the first reported collection of H. fluviatilis All sites are located
within the Western Uplands physiographic province, which has a complex bedrock
geology. Streambeds consist of gneiss, quartzite, and schist, mixed with varying
amounts of sandstone, dolomitic limestone, and shale. The northernmost sites drain
watersheds along the Housatonic Mountains. Suitable sites were based on similarity
to the physical properties of streams in Europe and the western US and Canada in
which Heribaudiella has been reported (Holmes and Whitton 1975, Wehr 2015, Wehr
and Perrone 2003, Wehr and Stein 1983). Key properties included a rocky substratum,
at least moderate current velocity (>10 cm s-1), and low turbidity (less than 10 NTU).
Based on these criteria, a reconnaissance survey determined that none of 5 sites along
Island Brook were suitable habitat for the species (samples also proved negative),
likely due to loss of solid substratum and highly turbid water. We identified sites near
and more distant from the original location to create a list of 43 candidate streams
in western Connecticut to sample. All had rocky substrata, averaged 5.4 m in width
Northeastern Naturalist Vol. 26, No. 2
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019
345
(min–max = 0.8–13.3 m), 23 cm depth (min–max = 7–42 cm), and 75% riparian
canopy cover (min–max = 21–93%). Details are in Appendices 1–3.
Methods
We obtained herbarium specimens of Holden’s 1898 material (as Lithoderma fluviatile
Aresch.) originally designated as item 536 in Fascicle IX of Phycotheca
Boreali-Americana (Collins et al. (1898) with permission from the University of
Michigan (MICH: 636207), Trinity College, CT (courtesy of C. Schneider), and
New York Botanical Garden (NY: 02137512, 02137513). The material was originally
dried onto mica slides and stored inside paper folders. We removed from each
specimen a small (less than 1 mm) fragment that we placed in a sterile 1.5-mL microcentrifuge
tube for transport to the laboratory.
We sampled streams in western Connecticut between June 2016 and October
2016 following standardized methods used by our laboratory (e.g., Grubaugh and
Wehr 2017, O’Brien and Wehr 2010). In each stream, we designated a 30-m reach
that included at least 3 riffle–pool associations. At each site, we removed and inspected
at least 20 rocks (where feasible) for the presence of any macroalgae (sensu
Holmes and Whitton 1975), and specifically, any obviously dark brown crusts that
might be later identified as Heribaudiella. When necessary, we used a field microscope
(Swift FM-31LWD; Swift Instruments, San Jose, CA) for confirmation. We
scraped algal material from at least 3 rocks into 15-mL or 50-mL centrifuge tubes
and placed them in an ice chest until return to the laboratory. We retained 1 cobblesized
rock (~10–20 cm) as a voucher specimen. At each site, we made a visual
estimate of the percentage of sizes of streambed substrata based on the Wentworth
scale (Cummins 1962). At locations where we collected rock samples, we measured
light availability as percent canopy cover using a Model C spherical crown densiometer
(Forestry Suppliers, Jackson, MS), current velocity using a Model 2000
Flo-Mate flow meter (Marsh–McBirney, Frederick, MD), stream width (m) with
a tape measure, and maximum depth (cm) with a meter stick. We measured water
temperature, pH, specific conductance, turbidity, and dissolved oxygen in situ using
a YSI ProDSS water quality meter (YSI, Yellow Springs, OH). We collected a
set of four 9-mL water chemistry samples for later chemical analysis after syringefiltration
(0.2-μm pore-size) and preservation to pH less than 2.0 as pe r USEPA (1987).
In the laboratory, we prepared algal material (dried herbarium sub-samples and
freshly collected material) for microscopy as described previously (Wehr 2015).
We rehydrated the dried material with deionized water on microscope slides for
~5 min prior to making observations. We compared the morphology and cell size
of the historical specimens with values published in recent floras (Eloranta et al.
2011, Wehr 2015), and modern-day material. We examined samples using a Nikon
Eclipse E600 interference microscope with Plan-Apo objectives, fitted with a DSFi2
(5 megapixel) digital camera (Nikon Instruments, Melville, NY). We analyzed
water samples for dissolved organic C (DOC) using a Shimadzu TOC-L analyzer
(Shimadzu, Columbia, MD), dissolved N and P with an Astoria A2 analyzer (Astoria,
Clackamas, OR), and dissolved Ca and Mg using a Perkin-Elmer 1100B
Northeastern Naturalist
346
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019 Vol. 26, No. 2
atomic absorption spectrophotometer in flame mode, following the manufacturer’s
guidelines(Waltham, MA). We followed EPA method 415.3 to measure DOC as
non-purgeable organic C (Potter and Wimsatt 2005). We measured dissolved N
as NH4
+ using the phenol–hypochlorite method, and NO3
- by the sulfanilamide-
NNED method after reduction of NO3
- to NO2
- in a Cd–Cu column (APHA 1985).
We measured inorganic P as soluble-reactive phosphorus (SRP) using the antimony-
ascorbate-molybdate method (APHA 1985).
We assembled the physical and chemical data in a spreadsheet and imported
these data into SYSTAT (v. 13; SYSTAT Software, Inc., Chicago, IL). Our primary
aim was to compare ecological conditions among stream sites and test for differences
in streams with and without Heribaudiella present. We tested all variables for
normality and homogeneity of variances prior to statistical analyses. We analyzed
those variables that conformed to these assumptions using a Student’s t-test; otherwise
we employed non-parametric tests (Mann-Whitney U; Sokal and Rohlf 2012).
We set the a priori Type-I significance level at P = 0.05.
We used boosted regression tree (BRT) analysis, a multivariate approach, to
describe the ecological niche of Heribaudiella in streams where it occurred. BRT
analysis is a model-free approach that employs decision trees to estimate complex,
non-linear effects of multiple predictors. We implemented a boosted regression tree
analysis (Elith et al. 2008), using the gbm.step function of the “dismo” package
(Hijmans et al. 2017). We employed an ad-hoc approach to tuning parameters to
identify a parameter set that produced low cross-validation deviance. This approach
led to a learning rate of 0.01, tree complexity of 10, and a bagging fraction of 0.9.
We averaged results from 100 runs with 10-fold cross validation.
Results
Examination of Holden’s 1898 collections
Microscopic examination of specimens from Island Brook revealed many
densely packed, dichotomously branched filaments, although plastids were not
easily distinguishable and pigments were faded (Fig. 1). Nonetheless, the general
morphology closely resembled that of H. fluviatilis with many remnants of the
multiply dichotomous-branched prostrate form (Fig. 1A, B). The thick-walled,
tightly packed vertical filaments that characterize the species were common in all
specimens examined (Fig. 1C). As noted by Holden on the original exsiccatae label,
we observed a few terminal unilocular sporangia (Fig. 1D, E); no plurilocular
sporangia were observed. Cells forming the vertical filaments were rectangular to
quadrate in shape and varied from 8 μm to 15 μm in diameter, comparing closely
with those we measured in live material (see details below).
Distribution and morphology of Heribaudiella in Connecticut
We surveyed streams in 4 western counties of Connecticut (Litchfield, Fairfield,
Hartford, New Haven), and discovered populations of Heribaudiella in 6 of 43
candidate streams, all located within westernmost part of Litchfield County (Fig. 2).
We observed no populations in streams within the Island Brook–Pequonnock River
watershed, from which the original (now extirpated) population was collected in
Northeastern Naturalist Vol. 26, No. 2
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019
347
1898. All streams in which we found Heribaudiella occurred in upland locations
more than 70 km from marine water. In the field, thalli occurred as circular, dark
reddish-brown crusts (~5–50 mm diameter) on boulders and cobbles (Fig. 3A, B).
Where it occurred, boulders typically had multiple colonies, but we observed none
on smaller stones. On boulders larger than 100 cm, several colonies commonly
expanded and coalesced to form more extensive patches. We found that not all
dark-colored crusts sampled were Heribaudiella. Several smaller dark crusts were
formed by the cyanobacterium Chamaesiphon geitleri Luther or Ch. cf. polonicus
(Rost.) Hansg., or by the green alga Gongrosira fluminensis Fritsch. Although some
crusts may be mistaken for Heribaudiella, cellular morphology and pigmentation
of this alga was distinctive.
Figure 1. Micrographs of Heribaudiella fluviatilis prepared from dried specimens collected
in 1898 by Isaac Holden from Island Brook, CT. (A, B): prostrate series of cells forming a
crust, (C): vertical series of tightly-packed upright filaments, (D, E): vertical filaments with
terminal (empty) unilocular sporangia. Herbarium sources: A and C from MICH; B from
Trinity College, CT; D and E from NY (all scale bars = 10 μm).
Northeastern Naturalist
348
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019 Vol. 26, No. 2
Microscopically, the morphology of Heribaudiella in Connecticut streams consisted
of a basal, broadly spreading prostrate form (Fig. 3C), which gave rise to a
vertical series of tightly packed upright filaments, some of which produced terminal
unilocular sporangia (Fig. 3D, E). We observed both the prostrate and vertical
forms in all collections. Sporangia released multiple zoospores (not shown). We
observed no plurilocular sporangia in any of the populations we collected. Cells
differed in size and shape between the 2 growth habits. The prostrate form consisted
of multiply-branched (dichotomously), thick-walled filaments composed of quadrate,
rectangular, or polygonal cells. Cell size varied widely: ~10–50 μm diameter
x 15–40 μm long, with cell walls 1–3 μm in thickness. The quadrate or rectangular
cells in the vertical series were more consistent in size (10–15 μm x 9–15 μm), but
the filaments themselves varied from 2 or 3 cells to more than 20 cells in length and
branched less frequently. Individually, cells contained numerous discoid goldenbrown
chloroplasts, and physodes, which are refractive storage bodies (Fig. 3E).
Ecological conditions
Geomorphological properties of the streams with and without Heribaudiella differed
in several respects. Those in which Heribaudiella occurred had a significantly
Figure 2. Map showing locations of stream sites in western Connecticut sampled for Heribaudiella
fluviatilis; filled circles = Heribaudiella present; open circles = Heribaudiella not
observed; asterisk (*) = original location of collection by Holden, now extirpated. Details
of site locations are given in Appendix 1.
Northeastern Naturalist Vol. 26, No. 2
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019
349
greater percentage of boulders in the streambed and greater depth, but significantly
lower specific conductance, than those in which Heribaudiella was not found
(Fig. 4). We detected no significant differences in streambed % cobble, % gravel,
Figure 3. Images of Heribaudiella fluviatilis collected from contemporary populations in
western Connecticut. (A): Brown macroscopic crusts on a large boulder in Gunn Creek
(scale bar = 5 cm); (B): close-up view of crusts on a rock from Macedonia Brook (scale
bar = 2 cm); (C): microscopic appearance of prostrate form with densely arranged, dichotomously-
branched filaments; (D): series of vertically arranged, tightly packed filaments
with terminal unilocular sporangia; (E): details of cells in vertical filaments with multiple
golden-brown, disc-shaped chloroplasts (scale bars C–E = 10 μm).
Northeastern Naturalist
350
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019 Vol. 26, No. 2
stream width, canopy cover, current velocity, or water temperature on the dates we
sampled. Nearly all streams were relatively small (mean width = 5.4 m ± 0.4 [SE]),
and well-shaded in summer (mean max depth = 75% ± 2.8 [SE]).
Water chemistry conditions differed among the streams in several key variables
(Fig. 5). Streams with Heribaudiella had significantly greater average pH (+ 0.40
units), 20% lower average dissolved NO3
- (-14 mg/L), and 60% lower average SRP
Figure 4. Physical
and geomorphological
characteristics
of sampled
streams with
( c r o s s - h a t c h e d
bars) and without
(open bars) Heribaudiella
fluviatilis.
(A): percentage
of streambed substrata;
(B): stream
width, maximum
depth, and % canopy
cover; and
(C): current velocity,
temperature,
and specific conductance
(details
in Appendix 1).
Significant differences
based on
Mann–Whitney U
test.
Northeastern Naturalist Vol. 26, No. 2
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019
351
(-17 mg/L) than in nearby streams lacking this species. We found no significant
differences in concentrations of dissolved Ca, DOC, NH4
+ (Fig. 4), or dissolved
O2 (not shown). The complete set of data is given in Appendices 1–3. BRT results
were well supported, with an average AUC of 0.99. BRT identified the variables pH,
boulder percentage, dissolved NO3
-, and SRP to have the highest relative influence
on the presence/absence of this species (Table 1). From these results, we characterized
the niche of Heribaudiella in this region as streams with an elevated pH, a high
percentage of boulders in the streambed, and low concentrations of dissolved NO3
-
Figure 5. Chemical characteristics of sampled streams with (cross-hatched bars) and without
(open bars) Heribaudiella fluviatilis. (A): streamwater pH, dissolved calcium, and dissolved
organic carbon; (B): streamwater dissolved NH4
+, NO3
-, and SRP (soluble-reactive phosphorus)
(details in Appendix 1). Significant differences based on Mann–Whitney U test.
Northeastern Naturalist
352
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019 Vol. 26, No. 2
and SRP (Fig. 6). However, while there was a significant difference in the depth of
streams with and without Heribaudiella (Fig. 4), this variable was not a significant
factor in the BRT model (Table 1).
Figure 6. Partial dependence plots, based on boosted regression tree (BRT) analysis for the
4 variables with the highest relative influence (indicated as a percentage below each plot)
of each variable on the response, after accounting for the average effects of all other variables
in the model. Higher values of the fitted function indicate more suitable habitat for
Heribaudiella fluviatilis.
Table 1. The relative percentage contribution of different predictor variables identified by the boosted
regression tree (BRT) model used to predict the main factors shaping the niche of Heribaudiella fluviatilis
in Connecticut rivers (11 most-important variables are listed in order from greatest to least;
values rounded to 2 decimal places).
Variable Percent contribution
pH 40.69
Percent boulder 27.44
Dissolved NO3
- 17.97
Dissolved SRP 10.00
Maximum depth 1.06
Percent riparian canopy cover 0.75
Specific conductance 0.66
Dissolved Ca 0.53
Current velocity 0.50
Dissolved NH4
+ 0.32
Temperature 0.07
Northeastern Naturalist Vol. 26, No. 2
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019
353
Discussion
The rediscovery of H. fluviatilis in Connecticut streams is notable because the
very first record of this alga on the North American continent was from a stream
in Island Brook, in Bridgeport, CT. This specimen was also part of an historically
important collection of algae—the Phycotheca Boreali-Americana (Collins et al.
1898)—now housed in several major herbaria (Sayre 1969, University and Jepson
Herbaria 2009). The specimens of H. fluviatilis represented the first and only record
of any freshwater member of the brown algae (Phaeophyceae) reported from North
America for more than 70 y. Eventually, two other phaeophyte species, Pleurocladia
lacustris A. Braun (Wilce 1962) and Sphacelaria lacustris Schloesser and
Blum (1980) were discovered, but no additional populations of Heribaudiella were
verified. That single record of H. fluviatilis in Connecticut stood for decades, until
Smith (1950) in Freshwater Algae of the United States, cast doubt on the identity of
Holden’s 1898 collection from Island Brook, due to its proximity to the high tide,
and suggested it was a different species from the marine flora. But later, collections
in western US and Canada in the 1980s, reignited interest in the species (Pueschel
and Stein 1983, Wehr and Stein 1985). After recent re-examination of dried material
from several exsiccatae, we determined (from co-occurring diatoms) that Holden’s
collections were from a true freshwater habitat, and that the original identification
was plausible (Wehr 2015). However, our survey, conducted 118 years later, found
that suitable habitats and extant populations no longer exist in Island Brook. In the
meantime, several populations of Heribaudiella have been uncovered in western
US states and Canadian provinces (Wehr 2015, Wehr and Stein 1985). One putative
eastern population was detected in a stream in Smoky Mountains National Park
(Johansen et al. 2007), but until the present study, evidence to support its inclusion
in the flora for New England remained unsettled. Our study now confirms that
H. fluviatilis occurs in at least 6 streams in western Connecticut, and thalli from
these locations are morphologically indistinguishable from populations in the western
US and Europe.
Our ecological data suggest that streams in this region in which Heribaudiella
occurs are relatively pristine, rocky systems with lower concentrations of dissolved
nutrients in the same region. Values measured in the present study are similar to
those found for Heribaudiella streams in British Columbia (Wehr and Stein 1985).
Average data in Connecticut compare favorably with the western streams with regard
to pH (CT: 7.9 ± 0.1, BC: 7.9 ± 0.4), dissolved calcium (CT: 33 ± 4, BC: 33 ±
13), SRP (CT: 11.5 ± 1.4, BC: 9.5 ± 5.2), and specific conductance (CT: 203 ± 26,
BC: 143 ± 94). Nitrate concentrations in Connecticut streams averaged somewhat
higher (CT: 60.3 ± 1.9, BC: 39.4± 28.2). The Connecticut data are also in agreement
with a large-scale bioassessment study in Norway that assigned H. fluviatilis a periphyton
index of trophic status (PIT) score of 4.98, which classified it as indicative
of relatively low total phosphorus concentration (Schneider and Lindstrøm 2011).
In a prior study, a niche analysis based on a canonical correspondence analysis
(CCA) of benthic macro algae in Austrian mountain streams similarly indicated
that H. fluviatilis was typical of higher pH, combined with lower NH4
+, NO3
-,
Northeastern Naturalist
354
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019 Vol. 26, No. 2
and SRP concentrations (Rott and Wehr 2016). The BRT analysis largely agreed
with previously published ecological descriptions, and together this indicates that
H. fluviatilis in Connecticut has a niche similar to that described for populations
found across the world. This information makes it possible to identify potential
new sites to survey for this apparently rare species. Based on water chemistry
variables, specific areas of the Northeast may be suitable for H. fluviatilis (e.g.,
Catskills, western New York, regions of Maine), where there is a mix of igneous
and carbonate-rich geology. While widespread globally, the species remains rare.
The local extirpation of H. fluviatilis from the Island Brook–Pequonnock River
watershed, and its presence on some European Red Lists for conservation status
suggest it may remain so (Temniskova et al. 2008, Wehr 2015). In addition, our
present data indicating a regional preference for less-disturbed streams with lower
nutrient levels suggest that the continued presence of Heribaudiella fluviatilis in
New England will depend on limiting future levels of anthropogenic disturbance to
streams in the region.
Acknowledgments
We thank Natalie Lynch and Yibing Zhou for assistance with field sampling and Kam
Truhn for assistance with chemical analyses. We thank the NY Botanical Garden Herbarium
(Kenneth G. Karol and Barbara M. Thiers), the University of Michigan Herbarium (Michael
Wynn, Richard Rabeler), and Trinity College (Craig Schneider) for loans of Collins’
specimens from the Phycotheca Boreali-Americana. This work was supported in part from
a Faculty Research Grant from Fordham University awarded to J.D . Wehr.
Literature Cited
Areschoug, J.E. 1875. Observationes phycologicae. Particula tertia. De algis nonnullis
scandinavicis et de conjuctione Phaeozoosporarum Dictyosiphonis hippuroidis. Nova
Acta Regiae Societatis Scientiarum Upsaliensis, Series 3 10(1): 1–36.
American Public Health Association (APHA). 1985. Standard Methods for the Analysis
of Water and Wastewater, 16th Edition. American Water Works Association, and Water
Environment Federation, Washington, DC. 1268 pp.
Collins, F.S., I. Holden, and W.A. Setchell. 1898. Phycotheca Boreali–Americana. Fascicle
XI, Malden, MA. 536 pp.
Cummins, K.A. 1962. An evaluation of some techniques for the collection and analysis of
benthic samples with special emphasis on lotic waters. American Midland Naturalist
67:477–504.
Elith, J., Leathwick, J.R., and T. Hastie. 2008. A working guide to boosted regression trees.
Journal of Animal Ecology 77:802–813.
Eloranta, P., J. Kwandrans, and E. Kusel–Fetzmann. 2011. Rhodophyta and Phaeophyceae.
P. 155, In K. Krammer and H. Lange-Bertalot. Süßwasserflora von Mitteleuropa, 7.
Spektrum Akademischer Verlag, Heidelberg, Germany. 311 pp.
Graham, L.E., J.M. Graham, and M.E. Cook. 2016. Algae, 3rd Edition. LJLM Press, Madison,
WI. 720 pp.
Grubaugh, C.R., and J.D. Wehr. 2017. Suitability of total nitrogen as a predictor of protein
content in stream periphyton. Freshwater Science 36:533–541.
Northeastern Naturalist Vol. 26, No. 2
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019
355
Hijmans, R.J., Phillips, S., Leathwick, J., and J. Elith. 2017. Package ‘dismo’. Species distribution
modeling. R package version 0.8–11. Available online at https://cran.rproject.
org/web/packages/dismo/dismo.pdf. Accessed 23 July 2018.
Holmes, N.T.H., and B.A. Whitton. 1975. Notes on some macroscopic algae new or seldom
recorded for Britain: Nostoc parmelioides, Heribaudiella fluviatilis, Cladophora aegagropila,
Monostroma bullosum, Rhodoplax schinzii. Vasculum 60:47–55.
Israelsson, G., 1938. Über die Süsswasserphaeophycéen Schwedens. Botanisk Notiser
1938:113–128.
Johansen, J.R., R. Lowe, S.R. Gomez, J.P. Kociolek, and S.A. Makosky. 2007. New algal
species records for the Great Smoky Mountains National Park, US A, with an annotated
checklist of all reported algal species for the park. Southeastern Naturalist 6(Special
Issue 1):99–134.
McCauley, L.A., and J.D. Wehr. 2007. Taxonomic reappraisal of the freshwater brown algae
Bodanella, Ectocarpus, Heribaudiella, and Pleurocladia (Phaeophyceae) on the basis of
rbcL sequences and morphological characters. Phycologia 46:429–439.
O’Brien, P.J., and J.D. Wehr. 2010. Periphyton biomass and ecological stoichiometry in
streams within an urban to rural land-use gradient. Hydrobiolog ia 657:89–105.
Potter, B.B., and J.C. Wimsatt. 2005. Determination of total organic carbon and specific UV
absorbance at 254 nm in source water and drinking water. Method 415.3. US Environmental
Protection Agency, Cincinnati OH. 56 pp.
Pueschel C.M., and J.R. Stein. 1983. Ultrastructure of a freshwater brown alga from western
Canada. Journal of Phycology 19:209–215.
Rott, E., and J.D. Wehr. 2016. The spatio–temporal development of macroalgae in rivers.
Pp. 159–195, In O. Necchi Jr. (Ed.). River Algae. Springer, New York, NY. 279 pp.
Sayre, G. 1969. Cryptogamae exsiccatae. An annotated bibliography of published exsiccatae
of algae, lichenes, Hepaticae and Musci. Introduction, I. General cryptogams, II.
Algae, III. Lichenes. Memoirs of the New York Botanical Garden 19:1–174.
Schloesser, R.E., and J.L. Blum. 1980. Sphacelaria lacustris sp. nov., a freshwater brown
alga from Lake Michigan. Journal of Phycology 16:201–207.
Schneider, S.C., and E.A. Lindstrøm. 2011. The periphyton index of trophic status PIT: A
new eutrophication metric based on non–diatomaceous benthic algae in Nordic rivers.
Hydrobiologia 665:143–155.
Smith, G.M. 1950. Fresh-Water Algae of the United States. McGraw–Hill, New York, NY.
719 pp.
Sokal, R.R., and F.J. Rohlf. 2012. Biometry, 4th Edition. W.H. Freeman, New Nork, NY.
937 pp.
Svedelius, N. 1930. Über die sogenannten Süsswasser–Lithoderman. Zeitschrift für Botanik
23:891–918.
Temniskova, D., Stoyneva, M.P., and I.K. Kirjakov,. 2008. Red List of the Bulgarian algae.
I. Macroalgae. Phytologia Balcanica 14:193–206.
US Environmental Protection Agency (USEPA). 1987. Handbook of Methods for Acid Deposition
Studies: Laboratory Analysis for Surface Water Chemistry. EPA 600/4–87/026.
US Environmental Protection Agency, Washington, DC. 168 pp.
University and Jepson Herbaria, University of California, Berkeley. 2009. Phycotheca
Boreali–Americana. Available online at: http://ucjeps.berkeley.edu/ina/pba/pba_main.
html. Accessed 10 July 2018.
Waern, M. 1952. Rocky-shore algae in the Öregund Archipelago. Acta Phytogeographica
Suecica 30:1–298.
Northeastern Naturalist
356
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019 Vol. 26, No. 2
Wehr, J.D. 2015. Brown algae. Pp. 851–871, In J.D. Wehr, R.G. Sheath, and J.P. Kociolek
(Eds.). Freshwater Algae of North America: Ecology and Classification. Elsevier, San
Diego, CA. 1050 pp.
Wehr, J.D. 2016. Brown algae (Phaeophyceae) in rivers. Pp. 129–151, In O. Necchi Jr. (Ed.)
River Algae. Springer International Publishing, Basel, Switzerland. 2 79 pp.
Wehr, J.D., and A.A. Perrone. 2003. A new record of Heribaudiella fluviatilis, a freshwater
brown alga (Phaeophyceae), from Oregon. Western North American Naturalist
63:517–523.
Wehr, J.D., and J.R Stein. 1985. Studies on the biogeography and ecology of the freshwater
phaeophycean alga Heribaudiella fluviatilis. Journal of Phycology 21:81–93.
Wilce, R.T., 1966. Pleurocladia lacustris in arctic America. Journal of Phycology 2:57–66
Northeastern Naturalist Vol. 26, No. 2
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019
357
Appendix 1. Geomorphological properties of sampled streams in western Con necticut. H. f. = whether H. fluviatilis was present.
% % % % % %
Stream name H. f. Date Lat. (°N) Long. (°W) bedrock boulder cobble gravel sand silt
Beacon Hill Brook No 14 July 2016 41.46882 73.04569 0 5 40 50 5 0
Bee Brook No 11 July 2016 41.68164 73.33296 0 0 40 10 0 50
Booth Hill Brook No 10 October 2016 41.24654 73.18161 0 5 80 10 0 5
Butternut Brook No 11 July 2016 41.75528 73.22434 0 80 10 3 3 4
Carse Brook Yes 30 June 2016 41.85562 73.37635 0 55 30 10 5 0
Clapboard Oak Brook No 23 June 2016 41.53053 73.38544 0 70 20 10 0 0
East Aspetuck River No 23 June 2016 41.59795 73.41533 0 5 90 5 0 0
East Br Naugatuck No 22 June 2016 41.83000 73.12003 1 69 10 5 15 0
East Br Silvermine Brook No 9 June 2016 41.94266 73.39066 0 1 4 85 8 2
East Spring Brook No 1 July 2016 41.61205 73.17574 0 10 60 20 5 5
Eight Mile Brook No 10 October 16 41.38903 73.16442 1 19 50 20 5 5
Finch Brook No 14 July 2016 41.56112 72.98357 0 30 50 10 0 10
Fullingmill Brook No 14 July 2016 41.50603 73.02987 0 20 70 5 5 0
Furnace Brook Yes 12 July 2016 41.81835 73.36811 5 60 20 10 5 0
Guinea Brook Yes 30 June 2016 41.82433 73.42987 0 45 50 5 0 5
Gunn Brook Yes 17 June 2016 41.80347 73.38287 5 80 5 5 5 0
Hancock Brook No 14 July 2016 41.65227 73.00767 0 40 0 40 10 10
Hop Brook No 14 July 2016 41.53447 73.10584 0 60 20 10 3 7
Horse Tavern Brook No 10 October 2016 41.21189 73.22380 0 0 70 20 10 0
Kent Falls Brook Yes 17 June 2016 41.76504 73.40873 0 50 40 5 5 0
Kirby Brook No 1 July 2016 41.62188 73.31631 0 10 80 5 0 5
Leadmine Brook No 22 June 2016 41.75358 73.06310 1 69 20 7 0 3
Little River No 9 June 2016 41.18326 73.21562 0 5 80 10 5 0
Long Meadow Brook No 14 July 2016 41.49757 73.09827 0 5 25 40 20 10
Lovers Lane Brook No 11 July 2016 41.81759 73.15599 5 70 15 5 0 5
Macedonia Brook Yes 17 June 2016 41.76024 73.49367 1 59 20 10 5 5
Merryall Brook No 12 July 2016 41.67541 73.44402 0 70 15 15 0 0
Northeastern Naturalist
358
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019 Vol. 26, No. 2
% % % % % %
Stream name H. f. Date Lat. (°N) Long. (°W) bedrock boulder cobble gravel sand silt
Mill Brook No 12 July 2016 41.84949 73.47830 0 1 60 19 10 10
Miry Brook No 15 June 2016 41.36363 73.50088 0 1 79 10 0 10
Mopus Brook No 15 June 2016 41.33410 73.54162 0 0 70 20 10 0
Moulthrop Brook No 11 July 2016 41.74864 73.20752 0 40 40 15 0 5
Nepaug River No 22 June 2016 41.83875 73.02312 0 20 50 20 10 0
Norwalk River No 9 June 2016 41.29886 73.27209 0 20 70 0 5 5
Padanaram Brook No 15 June 2016 41.43031 73.47976 10 30 50 5 5 0
Saugatuck River No 9 June 2016 41.19277 73.26066 0 70 15 5 5 5
Second Hill Brook No 23 June 2016 41.55312 73.34426 0 80 10 5 5 0
Spruce Brook No 22 June 2016 41.76634 73.15157 50 40 2 3 5 0
Still River No 15 June 2016 41.38914 73.47976 5 25 60 5 5 0
Sucker Brook No 11 July 2016 41.70274 73.34662 0 30 40 15 0 15
Tollgate Brook No 23 June 2016 41.57426 73.49972 0 15 60 15 10 0
West Aspetuck River No 12 July 2016 41.67159 73.39678 0 20 40 20 0 20
Wachocastinook Brook No 30 June 2016 41.98058 73.42306 0 1 90 10 0 0
West Redding Brook No 9 June 2016 41.33278 73.44255 0 10 30 50 5 5
Northeastern Naturalist Vol. 26, No. 2
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019
359
Appendix 2. Physical-ecological properties of sampled streams in western Connecticut.
H. f. = whether H. fluviatilis was present.
Stream Max Canopy Current
width depth cover velocity Temp. Turbidity
Stream name H. f. (m) (cm) (%) (m/s) (°C) (NTU)
Beacon Hill Brook No 8 22 57 0.55 19.5 0.9
Bee Brook No 6 12 86 0.47 19.7 3.5
Booth Hill Brook No 3 16 64 0.46 12.1 1.8
Butternut Brook No 7 26 85 0.47 17.5 2.9
Carse Brook Yes 4 30 86 0.70 19.4 3.2
Clapboard Oak Brook No 3 23 78 0.64 16.9 0.3
East Aspetuck River No 11 21 68 1.43 17.7 1.0
East Branch Naugatuck No 9 21 78 1.17 18.2 0.9
East Branch Silvermine Brook No 1 15 87 0.30 12.8 0.5
East Spring Brook No 7 37 76 1.04 18.4 1.0
Eight Mile Brook No 8 32 55 0.40 11.2 0.9
Finch Brook No 5 11 84 0.37 20.2 2.5
Fullingmill Brook No 13 27 83 1.20 19.9 1.2
Furnace Brook Yes 6 42 85 1.27 18.6 1.4
Guinea Brook Yes 5 17 28 0.50 22.5 2.4
Gunn Brook Yes 3 41 92 0.84 14.9 1.8
Hancock Brook No 5 39 72 0.52 22.3 5.1
Hop Brook No 8 23 21 1.07 21.0 1.5
Horse Tavern Brook No 6 17 72 0.25 11.6 1.9
Kent Falls Brook Yes 5 28 82 0.60 16.3 0.8
Kirby Brook No 4 16 76 0.59 16.9 0.8
Leadmine Brook No 5 31 80 0.60 16.5 0.7
Little River No 5 22 76 0.70 15.6 1.2
Long Meadow Brook No 4 20 86 0.25 22.7 1.2
Lovers Lane Brook No 4 24 93 0.70 17.3 1.0
Macedonia Brook Yes 5 25 91 1.11 15.5 5.5
Merryall Brook No 3 8 77 0.40 15.0 1.1
Mill Brook No 5 19 85 0.57 19.0 0.9
Miry Brook No 4 10 28 0.16 17.1 5.1
Mopus Brook No 3 13 68 0.46 21.2 2.6
Moulthrop Brook No 6 7 92 0.33 20.7 3.9
Nepaug River No 5 36 73 0.70 18.0 1.4
Norwalk River No 7 36 87 0.81 17.6 1.6
Padanaram Brook No 5 30 89 0.36 17.2 0.3
Saugatuck River No 8 29 74 0.68 17.6 2.1
Second Hill Brook No 4 14 84 0.48 14.9 0.8
Spruce Brook No 3 20 91 0.67 17.3 1.0
Still River No 8 32 86 1.08 18.9 2.3
Sucker Brook No 6 28 80 0.76 18.9 0.8
Tollgate Brook No 5 10 71 0.59 18.8 0.6
West Aspetuck River No 4 23 80 0.64 20.6 5.3
Wachocastinook Brook No 4 20 58 0.60 18.1 0.9
West Redding Brook No 2 15 74 0.46 16.9 1.6
Northeastern Naturalist
360
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019 Vol. 26, No. 2
Appendix 3. Chemical properties of sampled streams in western Connecticut . H. f. = whether H. fluviatilis was present.
Conductance Ca Mg NH4
+ NO3
- SRP DOC
Stream name H. f. (μS/cm) pH (mg/L) (mg/L) (μg N/L) (μg N/L) (μg/L) (mg P/L)
Beacon Hill Brook No 326.3 7.23 31.3 4.0 40.8 119.1 6.0 4.9
Bee Brook No 297.8 7.52 39.1 8.7 60.0 52.4 26.1 12.0
Booth Hill Brook No 273.0 6.91 15.6 4.1 13.6 64.0 7.4 15.9
Butternut Brook No 222.4 7.82 38.2 9.9 31.8 67.9 29.3 9.7
Carse Brook Yes 256.5 8.06 44.3 11.7 19.6 61.1 11.0 7.0
Clapboard Oak Brook No 379.6 7.65 61.0 16.2 11.3 89.2 2.1 3.8
East Aspetuck River No 384.0 8.21 52.2 14.7 27.0 89.7 21.9 5.0
East Branch Naugatuck No 237.5 7.37 25.7 5.1 28.9 69.8 6.4 5.0
East Branch Silvermine Brook No 447.1 7.43 68.2 19.2 91.4 87.7 37.4 7.5
East Spring Brook No 220.4 7.39 23.4 5.4 47.5 72.6 36.6 6.9
Eight Mile Brook No 215.9 7.29 18.7 4.7 8.5 61.1 6.5 12.3
Finch Brook No 397.6 7.47 43.2 4.9 10.2 137.3 29.7 19.7
Fullingmill Brook No 307.6 7.40 34.3 5.4 41.9 116.4 10.9 8.0
Furnace Brook Yes 288.6 8.16 45.4 11.4 55.3 55.4 16.7 23.0
Guinea Brook Yes 127.8 7.68 24.7 5.4 51.7 55.8 8.2 10.0
Gunn Brook Yes 232.2 7.85 33.7 10.4 52.9 66.1 15.0 8.0
Hancock Brook No 149.4 6.44 12.2 1.7 55.6 51.0 1.3 23.3
Hop Brook No 328.4 7.05 30.2 6.3 69.7 80.6 22.8 10.7
Horse Tavern Brook No 234.8 6.82 14.5 3.3 10.2 88.7 15.1 9.5
Kent Falls Brook Yes 152.1 7.68 22.7 5.6 29.5 65.4 8.9 3.9
Kirby Brook No 433.9 7.49 49.5 9.7 28.3 98.2 23.8 22.7
Leadmine Brook No 377.1 7.44 31.2 7.4 51.0 69.0 6.1 8.4
Little River No 200.5 7.16 22.0 4.8 52.1 62.6 8.3 5.5
Long Meadow Brook No 283.0 7.26 20.9 3.6 76.9 68.0 13.8 6.8
Lovers Lane Brook No 366.0 7.66 40.1 11.4 21.1 84.1 91.9 5.4
Macedonia Brook Yes 163.0 7.70 29.0 7.8 39.3 58.0 9.4 3.8
Merryall Brook No 309.4 7.95 54.3 15.6 15.6 95.9 32.0 7.4
Northeastern Naturalist Vol. 26, No. 2
J.D. Wehr, S.E. Steirer, and R.S. Sleith
2019
361
Conductance Ca Mg NH4
+ NO3
- SRP DOC
Stream name H. f. (μS/cm) pH (mg/L) (mg/L) (μg N/L) (μg N/L) (μg/L) (mg P/L)
Mill Brook No 455.2 8.13 80.2 23.4 15.1 69.3 15.3 43.2
Miry Brook No 444.9 7.25 69.8 14.6 158.7 65.3 17.1 6.7
Mopus Brook No 357.9 7.70 66.6 14.8 135.5 77.2 35.3 17.1
Moulthrop Brook No 224.0 7.39 34.4 8.1 79.9 51.1 11.6 6.5
Nepaug River No 137.0 7.50 16.1 3.0 34.8 75.5 19.0 8.2
Norwalk River No 651.0 7.64 84.0 21.0 79.9 62.6 192.1 11.2
Padanaram Brook No 495.0 7.61 65.4 14.0 52.5 81.6 15.1 11.2
Saugatuck River No 297.1 7.45 44.8 10.6 37.6 51.7 20.6 8.3
Second Hill Brook No 223.7 7.34 27.3 6.6 110.7 81.2 29.3 5.5
Spruce Brook No 150.6 7.44 17.8 4.3 21.6 65.0 4.7 6.6
Still River No 585.0 7.68 64.8 14.8 126.2 63.4 18.9 9.8
Sucker Brook No 287.7 7.91 36.2 8.4 32.5 68.6 38.4 7.6
Tollgate Brook No 369.4 7.75 46.3 10.2 64.4 75.3 139.8 6.9
West Aspetuck River No 254.6 7.06 41.5 9.6 41.8 19.7 33.2 21.7
Wachocastinook Brook No 92.3 7.63 19.2 3.2 18.7 65.1 4.6 3.5
West Redding Brook No 180.0 7.35 31.1 5.7 127.7 54.6 17.4 16.1