diff --git a/kerchunk/combine.py b/kerchunk/combine.py
index 376a8003..01dbca26 100644
--- a/kerchunk/combine.py
+++ b/kerchunk/combine.py
@@ -203,10 +203,11 @@ def append(
             target_options=target_options,
             asynchronous=True
         )
+        store = fs_as_store(fs)
         ds = xr.open_dataset(
-            fs.get_mapper(), engine="zarr", backend_kwargs={"consolidated": False}
+            store, engine="zarr", backend_kwargs={"consolidated": False}
         )
-        z = zarr.open(fs.get_mapper(), zarr_format=2)
+        z = zarr.open_group(store, zarr_format=2, use_consolidated=False)
         mzz = MultiZarrToZarr(
             path,
             out=fs.references,  # dict or parquet/lazy
@@ -373,8 +374,8 @@ def first_pass(self):
                 fs._dircache_from_items()
 
             logger.debug("First pass: %s", i)
-            z_store = fs_as_store(fs, read_only=False)
-            z = zarr.open_group(z_store, zarr_format=2)
+            z_store = fs_as_store(fs, read_only=True)
+            z = zarr.open_group(z_store, mode="r", zarr_format=2, use_consolidated=False)
             for var in self.concat_dims:
                 value = self._get_value(i, z, var, fn=self._paths[i])
                 if isinstance(value, np.ndarray):
@@ -399,11 +400,13 @@ def store_coords(self):
         """
         Write coordinate arrays into the output
         """
+        # group to write new refs to; backed by kv dict
         kv = {}
-        store = zarr.storage.MemoryStore(kv)
-        group = zarr.open_group(store, zarr_format=2)
-        m = fs_as_store(self.fss[0], read_only=False)
-        z = zarr.open(m, zarr_format=2)
+        store = zarr.storage.MemoryStore(store_dict=kv)
+        group = zarr.open_group(store, mode="w", zarr_format=2, use_consolidated=False)
+        # group to read coords from
+        m = fs_as_store(self.fss[0], read_only=True)
+        z = zarr.open_group(m, zarr_format=2, mode="r", use_consolidated=False)
         for k, v in self.coos.items():
             if k == "var":
                 # The names of the variables to write in the second pass, not a coordinate
@@ -454,6 +457,7 @@ def store_coords(self):
                 else:
                     arr.attrs.update(self.cf_units[k])
             # TODO: rewrite .zarray/.zattrs with ujson to save space. Maybe make them by hand anyway.
+        translate_refs_serializable(kv)
         self.out.update(kv)
         logger.debug("Written coordinates")
 
@@ -474,8 +478,8 @@ def second_pass(self):
 
         for i, fs in enumerate(self.fss):
             to_download = {}
-            m = fs_as_store(fs, read_only=False)
-            z = zarr.open(m, zarr_format=2)
+            m = fs_as_store(fs, read_only=True)
+            z = zarr.open_group(m, zarr_format=2, mode="r", use_consolidated=False)
 
             if no_deps is None:
                 # done first time only
diff --git a/kerchunk/tests/test_combine.py b/kerchunk/tests/test_combine.py
index 0cfb9505..37e841f8 100644
--- a/kerchunk/tests/test_combine.py
+++ b/kerchunk/tests/test_combine.py
@@ -9,6 +9,7 @@
 import kerchunk.combine
 from kerchunk.zarr import single_zarr
 from kerchunk.combine import MultiZarrToZarr
+from kerchunk.utils import refs_as_store
 
 fs = fsspec.filesystem("memory")
 arr = np.random.rand(1, 10, 10)
@@ -19,28 +20,28 @@
     dims=["x", "y"],
     name="data",
 )
-xr.Dataset({"data": data}, attrs={"attr0": 3}).to_zarr("memory://simple1.zarr")
+xr.Dataset({"data": data}, attrs={"attr0": 3}).to_zarr("memory://simple1.zarr", zarr_format=2)
 
 data = xr.DataArray(
     data=arr.squeeze() + 1,
     dims=["x", "y"],
     name="data",
 )
-xr.Dataset({"data": data}, attrs={"attr0": 4}).to_zarr("memory://simple2.zarr")
+xr.Dataset({"data": data}, attrs={"attr0": 4}).to_zarr("memory://simple2.zarr", zarr_format=2)
 
 data = xr.DataArray(
     data=arr.squeeze(),
     dims=["x", "y"],
     name="datum",
 )
-xr.Dataset({"datum": data}, attrs={"attr0": 3}).to_zarr("memory://simple_var1.zarr")
+xr.Dataset({"datum": data}, attrs={"attr0": 3}).to_zarr("memory://simple_var1.zarr", zarr_format=2)
 
 data = xr.DataArray(
     data=arr.squeeze() + 1,
     dims=["x", "y"],
     name="datum",
 )
-xr.Dataset({"datum": data}, attrs={"attr0": 4}).to_zarr("memory://simple_var2.zarr")
+xr.Dataset({"datum": data}, attrs={"attr0": 4}).to_zarr("memory://simple_var2.zarr", zarr_format=2)
 
 data = xr.DataArray(
     data=arr,
@@ -50,7 +51,7 @@
     attrs={"attr0": 3},
 )
 xr.Dataset({"data": data, "static": static}, attrs={"attr1": 5}).to_zarr(
-    "memory://single1.zarr"
+    "memory://single1.zarr", zarr_format=2
 )
 
 data = xr.DataArray(
@@ -61,7 +62,7 @@
     attrs={"attr0": 4},
 )
 xr.Dataset({"data": data, "static": static}, attrs={"attr1": 6}).to_zarr(
-    "memory://single2.zarr"
+    "memory://single2.zarr", zarr_format=2
 )
 
 data = xr.DataArray(
@@ -72,7 +73,7 @@
     attrs={"attr0": 4},
 )
 xr.Dataset({"data": data, "static": static}, attrs={"attr1": 6}).to_zarr(
-    "memory://single3.zarr"
+    "memory://single3.zarr", zarr_format=2
 )
 
 data = xr.DataArray(
@@ -82,8 +83,8 @@
     name="data",
     attrs={"attr0": 0},
 )
-xr.Dataset({"data": data}).to_zarr("memory://quad_nochunk1.zarr")
-xr.Dataset({"data": data}).to_zarr("memory://group1.zarr", group="group")
+xr.Dataset({"data": data}).to_zarr("memory://quad_nochunk1.zarr", zarr_format=2)
+xr.Dataset({"data": data}).to_zarr("memory://group1.zarr", group="group", zarr_format=2)
 
 data = xr.DataArray(
     data=np.vstack([arr] * 4),
@@ -92,8 +93,8 @@
     name="data",
     attrs={"attr0": 0},
 )
-xr.Dataset({"data": data}).to_zarr("memory://quad_nochunk2.zarr")
-xr.Dataset({"data": data}).to_zarr("memory://group2.zarr", group="group")
+xr.Dataset({"data": data}).to_zarr("memory://quad_nochunk2.zarr", zarr_format=2)
+xr.Dataset({"data": data}).to_zarr("memory://group2.zarr", group="group", zarr_format=2)
 
 data = xr.DataArray(
     data=da.from_array(np.vstack([arr] * 4), chunks=(1, 10, 10)),
@@ -102,7 +103,7 @@
     name="data",
     attrs={"attr0": 0},
 )
-xr.Dataset({"data": data}).to_zarr("memory://quad_1chunk1.zarr")
+xr.Dataset({"data": data}).to_zarr("memory://quad_1chunk1.zarr", zarr_format=2)
 
 data = xr.DataArray(
     data=da.from_array(np.vstack([arr] * 4), chunks=(1, 10, 10)),
@@ -111,7 +112,7 @@
     name="data",
     attrs={"attr0": 0},
 )
-xr.Dataset({"data": data}).to_zarr("memory://quad_1chunk2.zarr")
+xr.Dataset({"data": data}).to_zarr("memory://quad_1chunk2.zarr", zarr_format=2)
 
 data = xr.DataArray(
     data=da.from_array(np.vstack([arr] * 4), chunks=(2, 10, 10)),
@@ -120,7 +121,7 @@
     name="data",
     attrs={"attr0": 0},
 )
-xr.Dataset({"data": data}).to_zarr("memory://quad_2chunk1.zarr")
+xr.Dataset({"data": data}).to_zarr("memory://quad_2chunk1.zarr", zarr_format=2)
 
 data = xr.DataArray(
     data=da.from_array(np.vstack([arr] * 4), chunks=(2, 10, 10)),
@@ -129,11 +130,11 @@
     name="data",
     attrs={"attr0": 0},
 )
-xr.Dataset({"data": data}).to_zarr("memory://quad_2chunk2.zarr")
+xr.Dataset({"data": data}).to_zarr("memory://quad_2chunk2.zarr", zarr_format=2)
 
 # simple time arrays - xarray can't make these!
 m = fs.get_mapper("time1.zarr")
-z = zarr.open(m, mode="w", zarr_format=2)
+z = zarr.open_group("memory://time1.zarr", mode="w", zarr_format=2)
 time1_array = np.array([1], dtype="M8[s]")
 ar = z.create_array("time", data=time1_array, shape=time1_array.shape)
 ar.attrs.update({"_ARRAY_DIMENSIONS": ["time"]})
@@ -141,7 +142,7 @@
 ar.attrs.update({"_ARRAY_DIMENSIONS": ["time", "x", "y"]})
 
 m = fs.get_mapper("time2.zarr")
-z = zarr.open(m, mode="w", zarr_format=2)
+z = zarr.open_group("memory://time2.zarr", mode="w", zarr_format=2)
 time2_array = np.array([2], dtype="M8[s]")
 ar = z.create_array("time", data=time2_array, shape=time2_array.shape)
 ar.attrs.update({"_ARRAY_DIMENSIONS": ["time"]})
@@ -156,7 +157,7 @@
     dims=["time", "x", "y"],
     name="data",
 )
-xr.Dataset({"data": tdata1}).to_zarr("memory://cfstdtime1.zarr")
+xr.Dataset({"data": tdata1}).to_zarr("memory://cfstdtime1.zarr", zarr_format=2)
 fs.pipe(
     "cfstdtime1.zarr/time/.zattrs",
     b'{"_ARRAY_DIMENSIONS": ["time"], "units": "seconds since '
@@ -169,7 +170,7 @@
     dims=["time", "x", "y"],
     name="data",
 )
-xr.Dataset({"data": tdata1}).to_zarr("memory://cfstdtime2.zarr")
+xr.Dataset({"data": tdata1}).to_zarr("memory://cfstdtime2.zarr", zarr_format=2)
 fs.pipe(
     "cfstdtime2.zarr/time/.zattrs",
     b'{"_ARRAY_DIMENSIONS": ["time"], "units": "seconds since '
@@ -182,7 +183,7 @@
     dims=["time", "x", "y"],
     name="data",
 )
-xr.Dataset({"data": tdata1}).to_zarr("memory://cfstdtime3.zarr")
+xr.Dataset({"data": tdata1}).to_zarr("memory://cfstdtime3.zarr", zarr_format=2)
 fs.pipe(
     "cfstdtime3.zarr/time/.zattrs",
     b'{"_ARRAY_DIMENSIONS": ["time"], "units": "seconds since '
@@ -197,7 +198,7 @@
     name="data",
     attrs={"units": "months since 1970-01-01", "calendar": "360_day"},
 )
-xr.Dataset({"data": tdata1}).to_zarr("memory://cfnontime1.zarr")
+xr.Dataset({"data": tdata1}).to_zarr("memory://cfnontime1.zarr", zarr_format=2)
 fs.pipe(
     "cfnontime1.zarr/time/.zattrs",
     b'{"_ARRAY_DIMENSIONS": ["time"], "units": "months since 1970-01-01", "calendar": "360_day"}',
@@ -210,7 +211,7 @@
     name="data",
     attrs={"units": "months since 1970-01-01", "calendar": "360_day"},
 )
-xr.Dataset({"data": tdata1}).to_zarr("memory://cfnontime2.zarr")
+xr.Dataset({"data": tdata1}).to_zarr("memory://cfnontime2.zarr", zarr_format=2)
 fs.pipe(
     "cfnontime2.zarr/time/.zattrs",
     b'{"_ARRAY_DIMENSIONS": ["time"], "units": "months since 1970-01-01", "calendar": "360_day"}',
@@ -228,8 +229,9 @@ def refs():
 def test_fixture(refs):
     # effectively checks that single_zarr works
     assert "single1" in refs
-    m = fsspec.get_mapper("reference://", fo=refs["single1"], remote_protocol="memory")
-    g = xr.open_dataset(m, engine="zarr", backend_kwargs={"consolidated": False})
+    #m = fsspec.get_mapper("reference://", fo=refs["single1"], remote_protocol="memory")
+    store = refs_as_store(refs["single1"])
+    g = xr.open_dataset(store, engine="zarr", backend_kwargs={"consolidated": False})
     assert g.time.values.tolist() == [1]
     assert (g.data.values == arr).all()
     assert g.attrs["attr1"] == 5
@@ -274,7 +276,8 @@ def test_get_coos(refs, selector, expected):
     mzz.first_pass()
     assert mzz.coos["time"].tolist() == expected
     mzz.store_coords()
-    g = zarr.open(mzz.out, zarr_format=2)
+    store = refs_as_store(mzz.out)
+    g = zarr.open_group(store, mode="r", zarr_format=2)
     assert g["time"][:].tolist() == expected
     assert dict(g.attrs)
 
@@ -605,11 +608,11 @@ def test_chunked(refs, inputs, chunks):
         group="group" if "group" in inputs[0] else None,
     )
     # TODO: make some assert_eq style function
-    assert z.time.values.tolist() == [1, 2, 3, 4, 5, 6, 7, 8]
-    assert z.data.shape == (8, 10, 10)
-    assert z.data.chunks == chunks
+    assert z["time"].values.tolist() == [1, 2, 3, 4, 5, 6, 7, 8]
+    assert z["data"].shape == (8, 10, 10)
+    assert z["data"].chunks == chunks
     for i in range(z.data.shape[0]):
-        assert (z.data[i].values == arr).all()
+        assert (z["data"][i].values == arr).all()
 
 
 def test_var(refs):
@@ -774,9 +777,10 @@ def test_no_inline(refs):
     """Ensure that inline_threshold=0 disables MultiZarrToZarr checking file size."""
     ds = xr.Dataset(dict(x=[1, 2, 3]))
     ds["y"] = 3 + ds["x"]
-    store = fsspec.get_mapper("memory://zarr_store")
-    ds.to_zarr(store, mode="w", consolidated=False)
-    ref = kerchunk.utils.consolidate(store)
+    kv = {}
+    store = zarr.storage.MemoryStore(store_dict=kv)
+    ds.to_zarr(store, mode="w", consolidated=False, zarr_format=2)
+    ref = kerchunk.utils.consolidate(kv)
     # This type of reference with no offset or total size is produced by
     # kerchunk.zarr.single_zarr or equivalently ZarrToZarr.translate.
     ref["refs"]["y/0"] = ["file:///tmp/some/data-that-shouldnt-be-accessed"]
diff --git a/kerchunk/utils.py b/kerchunk/utils.py
index b8a53e3c..1f7e0258 100644
--- a/kerchunk/utils.py
+++ b/kerchunk/utils.py
@@ -48,7 +48,12 @@ def refs_as_store(
 
 def is_zarr3():
     """Check if the installed zarr version is version 3"""
-    return Version(zarr.__version__) >= Version("3.0.0.b2")
+    zarr_version = Version(zarr.__version__)
+    zarr_v3 = Version("3.0.0b2")
+    if zarr_version.is_prerelease:
+        return True
+    else:
+        return Version(zarr.__version__) >= zarr_v3
 
 
 def dict_to_store(store_dict: dict):
@@ -128,6 +133,7 @@ def consolidate(refs):
                 out[k] = (b"base64:" + base64.b64encode(v)).decode()
         else:
             out[k] = v
+        out = translate_refs_serializable(out)
     return {"version": 1, "refs": out}
 
 
diff --git a/kerchunk/zarr.py b/kerchunk/zarr.py
index ea0612de..0417d965 100644
--- a/kerchunk/zarr.py
+++ b/kerchunk/zarr.py
@@ -54,6 +54,7 @@ def single_zarr(
     if isinstance(refs, LazyReferenceMapper):
         refs.flush()
     refs = kerchunk.utils.consolidate(refs)
+
     return refs